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What’s all the fuss with Mirror Neurons?

Admin — Sun, 27 Jun 2010 17:51:51 +0000

Mirror neurons have been in the news a lot lately, performing a dizzying array of functions, from the fight against pornography to explaining why World Cup Football is a good thing, to explaining the banking crisis. It seems like people love to use mirror neurons to explain just about anything they want to, it doesn’t really matter what. And they don’t seem to know a whole lot about mirror neurons, other than vague associations with “empathy” and “imitation”. These are common enough things in human affairs that mirror neurons can intrude anywhere, make any opinion seem more scientific.

This profligacy is not limited to lay people and journalists. Scientists have implicated them in things as varied as understanding intentions, empathizing with others, the development of language, a possible role in autism, and a host of other things. Hundreds of papers on these subjects have been published. Can mirror neurons indeed have such near-miraculous explanatory powers?

What are Mirror Neurons?

What are mirror neurons, and why all this fuss about them? In brief, mirror neurons are certain neurons in the brain that fire not only when the individual performs an activity, but also when the individual observes someone else perform that activity. They were discovered in the 90’s by an Italian scientist named Giacomo Rizzolati, in the macaque monkey. He observed that in the F5 region of the monkey brain (part of the premotor cortex, a region concerned with planning actions); there was a certain population of neurons which had some peculiar properties:

They fire both when the monkey performs an action, and when the monkey sees another monkey (or human) perform that same action. Typical actions in which such activity is observed are things like reaching for an object, or grasping an object.
They fire only when the actions are goal-oriented, meaning when there is a perceptible goal to the action, some object towards which the action is directed, for example, reaching for food. They do not fire when the monkey observes another monkey performing meaningless actions, such as waving its arms randomly.
Further, they fire only when the monkey knows what the goal is. Performing a pantomime (reaching for food when food is not there) will not produce any activity in these neurons. However, if the monkey knows the object is there even though he cannot see it, then they will fire. For example, if the observing monkey sees the food, but then a screen is placed in front of the food, and he sees the acting monkey reach for the food behind the screen, these neurons will fire, even though the object (food) is itself hidden at the time. This is because the monkey saw the food previously, and knows it’s there.
They don’t fire when tools are used to perform the actions. For example, if food is delivered simply by pressing a button, there is no activity in the mirror neurons when this is observed. Only the observation of direct, goal-oriented action will provoke the activity of the mirror neurons.
They don’t respond to partial activity. They won’t fire if you show the monkey the food, or show the monkey another monkey looking at the food. Only when the other monkey reaches for the food will they fire in the observing monkey. Further, the response is quite specific for the type of activity. For example, consider two actions – reaching for an object and placing it in one’s mouth (as with food), and a different action, picking up an object and placing it in a container. Both are goal-directed activities, and both can generate mirror neuron responses in the observer, but different populations of neurons are involved in each response. The mirror neurons which fire when the monkey observes another monkey reaching for food and placing it in its mouth are different from the mirror neurons which fire when the monkey observes another monkey picking up some object and placing it in a box.
The neurons will fire as early as the initiation of activity (as soon as the monkey observes another monkey initiating the activity), even before the action is complete. In other words, they fire as soon as the monkey observes another monkey reaching for the food, before it has actually reached the food, grasped it, brought it back to its mouth, and deposited it there. Now it’s possible that some actions could be ambiguous, for example, a monkey may reach for an object either to place it in its mouth, or to place it in a box. However, in most tested examples where the activities are clearer cut, the appropriate population of mirror neurons for that activity begins to fire at the initiation of that activity, suggesting that the observing monkey is predicting the subsequent course of the action.
They don’t fire during imitative activities. Adult macaque monkeys do not imitate, but juvenile ones do. Imitation is not a “goal oriented” action in the previous sense. A juvenile monkey will imitate any meaningless action, for instance, if you stick your tongue out at it, it will stick its tongue out back at you. In juvenile macaques, mirror neurons do not fire during imitative activities – not during observation of the activity, and not during subsequent performance of that activity.
They don’t fire in preparation for the activity, only when the activity occurs. This is important because there are areas nearby in the monkey brain (for example, area 6) which have “set neurons” that fire in anticipation or preparation for an action, before the action is initiated. This is not true for mirror neurons.
They don’t seem to represent covert activity, that is, activity which happens in the brain but is not implemented by the body. More specifically, covert activity would be the brain going through the motions of reaching for an object, and yet the hands don’t move, the monkey doesn’t actually reach for the object. Covert activity is ruled out by the observation that during the mirror neuron firing, there is no corresponding activity in the primary motor cortex. For covert activity, one would expect some activity in the primary motor cortex, which does not get translated into movement of arm muscles because it’s sub-threshold, or because it’s blocked in some way. Such covert activity is not recorded.
Finally, it’s important to remember that mirror neurons are only a subpopulation of the neurons in the F5 area. Different estimates put them at somewhere around 20%-40% of population. The rest of the neurons in F5 which do not show mirror activity are called “canonical” neurons. Of the subpopulation of mirror neurons, some might respond only to visual stimuli, some only to auditory, and some only to somatic sensory information. Further, of those that respond to say visual stimuli, some might respond only to certain kinds of actions and others to a different kind of action, as mentioned earlier.

These observations on macaque monkeys were the basis of our understanding of mirror neurons. Any theory about mirror neurons must explain these observations. So, what are these mirror neurons, what are they doing, and why?

Rizzolati and others initially explained mirror neurons as a form of “action understanding”. In Rizzolati’s words:

“Each time an individual sees an action done by another individual, neurons that represent that action are activated in the observer’s premotor cortex. This automatically induced, motor representation of the observed action corresponds to that which is spontaneously generated during active action and whose outcome is known to the acting individual. Thus, the mirror system transforms visual information into knowledge.”

Nielsen put it this way:

“A mere visual representation [of an action], without involvement of the motor system, provides a description of the visible aspects of the movement of the agent, but does not give information critical for understanding action semantics, i.e., what the action is about, what its goal is, and how it is related to other actions.”

What does this mean? They are basically saying that in a pre-language sense, our brain has a certain innate “vocabulary” which it uses in planning. Part of this vocabulary has to do with motor actions, and that is assisted by mirror neurons. So for example, our brain has a “word” or a “concept” or a “symbol” or some discrete “thing” (to be as non-committal as possible) which represents the action of grasping, and that mirror neurons are an automatic mechanism that identifies this action when we observe others do it. By activating the same neurons that we would activate if we ourselves performed this act, we can recognize or identify when others are doing it. This adds to our knowledge in some sense – by observing the other monkey stretch its arm out and grasp the food, we gain the knowledge that the monkey is going to eat the food, because our mirror neurons are firing in the pattern in which they would if we were to reach for the food and grasp it.

This is an interesting point to consider, especially if we generalize it beyond monkeys to humans. But before we do that, let’s consider a few problems with the monkey model. Biology is very messy, and for every case where someone says “X”, another person says “not-X” and often the evidence for both is inconclusive. So what are some of the objections against this “action understanding” theory?

First, there is some evidence that disruption of the F5 area (the mirror neuron area postulated to be involved with “action understanding”) does not disrupt “action understanding”. That is, if you destroy the area supposedly responsible for this function, the function does not go away. This is sort of fuzzy, because some experiments seem to show that lesions of F5 do indeed disrupt some forms of action understanding, while others don’t support the idea. So I’ll leave this alone for now until we have more data.

Second, we know that action understanding can happen without mirror neurons. The visual system has the job of identifying objects we see, understanding relationships between them, and using that information as the basis for action. This can occur quite independently of F5. For example, the Superior Temporal Sulcus (STS) has cells which are much more sophisticated than the F5 mirror neurons in distinguishing between different types of observed actions, and they respond strongly when monkeys observe other people do various actions. They don’t, however, have a motor component. They do not fire when the monkey himself does the action. So it’s possible to have action understanding without the corresponding motor part.

Third, it now seems that there are mirror neurons in the monkey’s M1 region, or primary motor cortex. This is a problem because we assumed that mirror neurons aren’t simply responding to a covert action, they are actually helping us process information by helping us identify the actions of others. One thing that supported this view was that there was no activity in the primary motor cortex when one monkey observes another monkey act. But now that we know that there are mirror neurons in M1, this foundation is somewhat shaken, and it’s harder to rule out that what we are seeing is simply an associational covert action. Humans do this too, if you observe a sports fan watching his favorite game on TV. He will contort his body into actions mimic the player he’s observing, almost “willing” the player to respond as he does. This does not need to be explained via “action understanding”, but simply by the fact that the sports fan is reacting as he thinks the player ought to act. He may in fact act differently from the player on the screen, because in his judgment a different action was called for.

Mirror Neurons in Humans

This brings us into the problem of generalizing from macaques to humans. While there is some evidence that humans also have mirror neurons, there are a number of key differences, including:

Humans show “mirror neuron” activity even for imitation, while monkeys do not. Monkeys only show activity when the action is goal directed, not when it’s random.
Humans react to pantomime displays, while monkeys do not. When the object isn’t really there, but the actor does a good enough job of pretending that it is, humans will show mirror neuron activity as if the missing object were really there. Monkeys don’t do that. They need to know that the object is there, even though it may be hidden during the experiment.

Some researchers explain these discrepancies by saying that the human system is more “evolved” and responds to a wider range of stimuli. This may be so. However, it raises two problems. First, it shows that there are significant differences between humans and monkeys in this regard, and therefore research that was done on monkeys should not be uncritically generalized to humans, as it often is. Second, it weakens the original argument for monkeys, which was that mirror neurons are responsible for “action understanding”. Imitative or random behavior is obviously not goal directed in this sense, and therefore there is nothing corresponding to understand. Why then, are human mirror neurons activated in such cases?

The data for humans and monkeys isn’t easy to compare. There are a lot of studies at the single cell level with implanted electrodes that are available for monkeys. Parallel data for humans is non-existent or very scarce, because of the obvious problems with implanting electrodes into human research subjects. On the other hand, there is a wealth of human fMRI data, which is scarce for monkeys, because monkeys can’t easily be trained to perform tasks inside an MRI scanner. This imbalance of the data types makes direct comparisons difficult.

Some tests which can only be performed on humans show other differences as well. For example, Catmur et al performed a TMS/MEP study on human subjects (TMS is trans cranial magnetic stimulation, in which a part of the brain is stimulated with magnets placed on the outside of the skull. MEP is motor evoked potentials, which are small electrical signals recorded from peripheral nerves) which show dissociation between mirror neurons and “action understanding”. The experimental setup was to stimulate specific motor areas of the brain (through TMS) to produce a twitching of the abductor muscles of the hand and fingers (which was recorded by MEP). Under the standard test condition, the subjects watched a video of someone abducting the index finger of hand, followed by abducting the little finger. When the subjects were watching the video of the index finger being abducted, the MEPs recorded from their own index fingers were stronger than those recorded from their little fingers. When they observed videos of someone abducting his little finger, the MEPs recorded from their little fingers were stronger than those recorded from their index fingers. This was the standard response. However, in the test condition, this was reversed. The subjects were trained to trained to move their index finger when they saw the video of someone moving his little finger, and vice versa. After training, the MEPs recorded were reversed. In other words, the “mirror effect” dissociated from the “action understanding”. Given that this is a crude way to compare what was done will skull electrodes in monkeys, but it is still significant.

This sort of training to overcome default congruent behavior is very common among humans. The fact is that we don’t WANT to act exactly the way we observe someone else acting. If you see the same action, say someone tossing a ball at you, your action will be very different depending upon whether you have a bat in your hand, or if you are the catcher. Our expectation of what they are trying to do depends upon our own role and circumstances. How do monkeys deal with this? We don’t know.

The large numbers of fMRI studies have opened up many interesting areas for study in humans. By its nature, fMRI scans large parts of the brain, compared to the single cell recordings done in monkeys. When you are scanning large areas of the brain, other interesting things turn up. Humans apparently have mirror type neurons in many locations. Among the more interesting regions are the anterior cingulate cortex, the anterior insula, and the inferior frontal cortex. These areas are supposed to have roles in mediating emotions, which leads to the speculation about empathy.

Mirror Neurons and Empathy

We know that observing a certain emotion in others can produce the same emotion in ourselves. This has been amply demonstrated in several studies for emotions such as disgust and pain. Further, when we observe someone else feeling these emotions, there is increased activity in areas of the brain (the above mentioned areas) which are activated when we ourselves experience those emotions. This is strong evidence for mirror neurons in these areas.

There are supportive studies as well. People who self-report to having a high empathy in questionnaires show a greater mirror neuron activation of emotion centers in the brain in fMRI when they are exposed to images of other people feeling those emotions, compared to people who self-report to having lower empathy. Further, not only do the self-reporting empathic people show greater activation in areas to do with emotions, they also show greater mirror neuron activation in tests which have nothing to do with emotions, such as the reaching/grasping tasks described earlier. Does this mean that some people just have a stronger mirror neuron system, which they typically experience as “having more empathy”?

There is some evidence in support of this from the opposite end of the spectrum too. Some autistic people (who have very low empathy) have been found to have markedly smaller/thinner cortical regions that are associated with mirror neurons. Autistic people also generally show lower mirror neuron activity in fMRI and EEG experiments. However, the implications of these findings are disputed, and the matter is not settled.

Mirror Neuron Fever in the Media

While this is extremely fascinating stuff, the fact is that our theories about the role and function of mirror neurons are very hazy at this point. Many of the theories were built on monkey models, which have not been proven to apply to humans. In fact, there are a number of ways in which human mirror neurons are different from monkey mirror neurons, so we should not expect the monkey data to simply generalize to humans without modification. These details are often ignored by media and even by scientists, who have a poor understanding of mirror neurons.

For example, consider this article in the Washington Times about a group lobbying Congress to ban porn because of the effect it might have on children. They found a doctor, a “forensic pediatric physician” to bolster their case.

Quoting from the article:

Pornography normalizes sexual harm, Dr. Cooper said. It shows children a lack of any kind of emotional commitment or relationship between two consensual partners, shows unprotected sexual contact and visual examples often of violent rape.

When a child sees this image of adult pornography, the mirror neurons that are in their brain will convince them that they are actually experiencing what they are seeing,” she said.

Children are very vulnerable as compared to adults because of the presence of mirror neurons in the brain, Dr. Cooper said. Mirror neurons are part of the brain that convince us that when we see something we are actually experiencing it.

This is complete nonsense. It is in fact the opposite of what the theories about mirror neurons say. We don’t experience stuff because we see it, we experience stuff when we do it, and then this knowledge can later be used to understand the actions of another. You don’t experience playing a piano just because you see someone else playing a piano, if you have never played a piano yourself. This is the whole point of mirror neurons – that our brains can and do obtain information and make sense of it in many different ways. On an intellectual and analytical level, we can observe a person playing a piano, understand what he’s doing, get some sort of “action understanding” from the observation. If, however, we ourselves have played the piano before, then to this analytical understanding we can add an “experiential” understanding, and perhaps understand better what it feels like to play the piano, and to understand the person we are observing from an experiential level in addition to an analytical level. Even this is just a theory, and is by no means widely accepted. But to go from this to saying that mirror neurons can convince us that we are experiencing what we see someone do is supremely ridiculous. And then to add that “children are very vulnerable as compared to adults because of the presence of mirror neurons in the brain” is a gratuitously stupid statement. Why would children be more vulnerable compared to adults because of mirror neurons? Because they have mirror neurons while adults don’t? No, adults have them too. Because they have more mirror neurons than adults? No, they don’t. All of which assumes that mirror neurons enable these kids to experience what they see on the screen, which is a wrong conclusion based on a poor understanding of mirror neurons.

This is an obvious example of political activism misusing science to push an agenda, but not all such incidents are so obvious. There are plenty of scientists who have caught on to the mirror neuron idea as well, and use it to push their pet theories. Among the worst offenders are “evolutionary biologists”, which is a category that is fast becoming known for having miles of speculation hanging on to an inch or two of fact.

Mirror Neurons and Morality

One common theory these days is that mirror neurons explain how humans evolved a moral code. The idea is that since we can empathize and feel another’s pain, we know when he’s feeling bad. And for various reasons ranging from social cohesiveness to “seeing him feel bad makes me feel bad”, we came up with the idea that we shouldn’t make others feel bad. This, supposedly, became the basis for some sort of golden rule – don’t do stuff to others that would make you feel bad.

I know this sounds very simplistic, and certainly there are many people who express the same idea much more eloquently, but this is in essence what it amounts to. I have some serious problems with this idea.

First, I am not denying that mirror neurons are real. Of course they are. Second, I am not denying that they may have a role in empathy, in understanding how others feel because we can experientially know their emotion since we feel it ourselves. There are plenty of studies which support that too. However, as a basis for morality, this explanation is very lacking.

Mirror neurons are only one of the ways in which we know things about other people. As mentioned earlier, we have much more sophisticated systems (such as the STS) which allow much finer discrimination when judging and interpreting the actions of others. These systems are not based on mirror neurons at all. Secondly, there are many ways of learning that if you hit someone, he will probably hit you back. While it may help to know “oh, that must have hurt him, I know because I’ve felt pain myself” this knowledge is general enough that we don’t need mirror neurons to remind us of it constantly. If you’ve bumped your toe against a rock, you know it hurts. This does not require mirror neurons. It is not a stretch from that to understand that if you hit someone else with a rock, it will hurt him too. Mirror neurons can add to that, for example by seeing the grimace on his face once he gets hit, which may help you understand the extent and severity of his pain better after you have hit him. If you are empathic, you may feel some pain yourself, from watching his reaction. But nowhere near the pain he felt. And the fact is, while it may have added something to your knowledge, you certainly knew beforehand, before hitting him, before watching him grimace, that it would hurt. That’s probably why you hit him in the first place, to make him hurt.

Now if empathy was strong enough that our own distress while watching someone else in pain would prevent us from hurting anyone, then we might have an argument. But it isn’t. Even the kindest, most empathic mother may occasionally slap her child for misbehavior. We know from experimental studies that empathy (and the corresponding mirror neuron activation) increases towards people we love. So if it’s still not strong enough to prevent us from hurting people we love, how would it prevent us from hurting those towards whom we are indifferent?

On the other hand, there are several ways in which we can derive the same morality without referring to mirror neurons, which make much more sense. For example, we know that if you hit someone, he might hit back. This dissuades us from hitting people very frequently, because the consequences to ourselves would be unpleasant. We also know that if we live in a family where two people are constantly fighting each other, it can get unpleasant for other family members as well. You don’t want to deal with angry individuals, even though they might not be angry specifically at you. This is why when humans live in social groups, as our ancestors did, it benefits everyone to see that peace is maintained, even those who are not involved in the fighting. These are common sense things that we all know. And they are powerful inducements towards “morality”, if morality is reduced to “don’t hurt other people” in mirror-neuron fashion. And this kind of analysis is available to everyone without any mirror neuron imperatives.

The second and more important question to me is whether “don’t hurt people” is a sufficient basis for morality. Or even a particularly good basis. I don’t think it is. Most of us require a concept of justification when it comes to morality. Someone might perform an action and feel bad about it, and through empathy, we may observe this person and feel bad ourselves because he feels bad. But we may still think that he deserves to feel bad, because of the nature of his actions. This is the essence of justice, which is really the foundation of our morality. A killer may feel bad because society locks him up; we may look upon his face and see fear and misery on it, and perhaps that will evoke fear and misery in our own minds. But our idea of morality might be that he deserves his fate, because he took a life. You can call that balancing empathies, if you will – empathy towards the victim versus empathy towards the killer. But if it is empathy, it’s not based on mirror neurons. We don’t have to see the killer’s face, we don’t have to observe the act of the murder, and we don’t have to see his victim’s face. None of the things that mirror neurons might have a role in are required. All you need are analytical concerns, such as “is this justice” or “he can’t kill anyone else if he’s locked up”.

You can ask the same question in another way. If you cheat on your spouse, and you know that your spouse will never find out, is it okay? If your sole concern was empathy and “don’t hurt people”, then you might consider it okay, since your spouse will never find out and never be hurt by your action. However, many people might disagree based on other grounds. Such as, you promised to be faithful. Why should you keep your promise? If you do, I think it’s because you value integrity. That is the crux, not empathy.

So I don’t consider empathy to be a sufficient basis for morality. Considerations like justice and integrity, concern for the viability of the society in which you live by having rules that promote harmony – these are all essential for a system of morality. And as mentioned earlier, empathy isn’t the greatest or most powerful reason for the golden rule either. As the rule itself says “do unto others as you would have them do unto you” – meaning, the stress is on the consequences, on the “as you would have them do unto you”. What are the implications? That if you want to be treated right, you better treat others right. If you expect consequence Y, do action X. Why? Because that’s justice. Empathy is part of it, but by no means the only part. Nor is empathy even necessary to understand that people might feel bad if you treat them badly.

Mirror Neurons and Philosophy

Finally, I’d like to touch on some philosophical implications of mirror neurons, which I think are pretty exciting. One well known fact (and problem) in philosophy is that each of us only ever has access to his own mind. We never really know what another person experiences, what they feel. We can draw inferences from their behavior, but we cannot directly experience what they experience. This leads to philosophical views that can verge on the absurdly solipsistic – “I am the only person, everyone else is just an entity that responds in certain ways to certain things I do or observe. Perhaps they are not even real; perhaps they are just creations of my mind”.

There is no cure for true solipsism. If everything is a figment of your imagination, then you have no possible way to establish the reality of anything but your own mind. This is technically true, but uninteresting, since it leads nowhere. At best, you have to admit that the figments of your imagination behave in somewhat predictable ways, just as they might if they were real. Whether you continue to call them figments of your imagination or real make little difference to how you behave. If you believe that truck you are imagining can kill you, then you will move out of its way whether it’s real or not. It becomes an exercise in semantics.

However, there is a kernel of a real problem here. Even if we admit that other people exist, we don’t know what goes on inside their minds. There are many approaches people take to overcome this – by making certain assumptions (he’s a human like I am, with the same sort of machinery to think, reason, feel, that I do), and we can interpret their behavior in light of our own experiences. However mirror neurons provide an extra link in this chain. If mirror neurons allow us to experience what the other person experiences more directly, then this is an automatic connection between his brain and ours, in that we have within our own brains a parallel to what is happening inside his brain. By becoming aware of these parallels in our own minds, we have some sort of understanding that is more experiential than simply observing his behavior.

Australopithecus sediba – a new human ancestor?

Admin — Thu, 08 Apr 2010 21:09:30 +0000

An interesting story has been making the rounds in the science press today – the unveiling of new hominid fossils, by Lee Berger, of the University of Witwatersrand in South Africa. In two related articles in Science, Berger and colleagues have tentatively classified these as belonging to a new species: Australopithecus sediba.

The fossils represent two individuals – a juvenile male and an adult female, and there is some evidence that these two individuals were associated in life (perhaps mother and son). The skeletons are remarkably complete, even in comparison to such well known specimens as Lucy. An almost complete skull, mandibles, part of a pelvis, and a complete collar bone are included, as well as limb bones, fragmented ribs, and some vertebrae.

Fossils of two individuals (juvenile male on left, adult female on right) of Australopithecus sediba. From Berger, et al "Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa" Science, April 9, 2010.

The fossils date from between 1.8 to 1.95 million years old, which makes them very exciting, since fossils from this period are rare. This is also the period when the genus Homo differentiated from australopithecines, and may therefore cast some light on the otherwise hazy ancestry of Homo.

The original paper in Science (full text available with free registration at their site) describes the fossils in great detail, but the interesting features seem to be:

Skull: A. sediba is different from earlier australopithecines in being less prognathous, having a generally thinner and lighter jaw, smaller teeth. These are all characteristics trending towards Homo. In contrast, the cranial capacity has been estimated to be about 430 cc, which is smaller than the lowest currently accepted range of early Homo (510 cc).

Postcranial: The rest of the skeleton is much like earlier australopithecines, with two significant differences. First, the legs are quite long, making A. sediba somewhat taller than earlier australopithecines (estimated height about 4.5 feet). Second, the pelvis appears to be more adapted for walking. Again, both of these traits seem to foreshadow Homo. In contrast, the arms are long and australopithecine-like, as is much of the rest of the skeleton.

Australopithecus sediba skull. From Berger, et al "Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa", Science, April 9, 2010.

Given this mix of australopithecine and early Homo traits, it was not clear whether these fossils represent a late australopithecine or an early Homo. The authors have chosen to classify them as a new species of Australopithecus, and they go over their reasons in great detail in the paper. I am not qualified to comment on their merit, but from a quick glance at various commentaries on the paper it seems that the anthropological community is divided on the issue.

So why is this issue important and what does it all mean? Well, first we need to understand the context of this discovery. The larger context is the appearance of Homo. This is not well understood. The earliest member of the genus Homo is generally considered to be Homo habilis. According to the fossil record, H. habilis appeared about 2.3 million years ago, and is hence older than these fossils. However, because of the fragmentary nature of the early remains, it is difficult to be sure that the early remains do in fact represent Homo. The better known and more complete skulls, such as OH 7, OH 24, KNM ER 1805 and KNM ER 1813, are all about 1.7 to 1.9 million years old. For a while, anthropologists did not even agree whether H. habilis represented a separate species, preferring to classify skulls as either australopithecine, or those of H. erectus. These days, H. habilis is more accepted, but because of the wide variation in H. habilis fossils, many people believe that they represent more than a single species. H. rudolfensis is possibly a second ancient species of Homo, with one skull (KNM ER 1470) being dated to about 1.9 million years old.

Secondly, there is the matter of the persistence of H. habilis. According to the fossil record, H. habilis persisted as late as 1.4 million years ago. This means that for about half a million years, H. habilis co-existed with H. erectus, which is generally reckoned to have descended from H. habilis. Of course, this can be explained by punctuated equilibrium (some population of H. habilis, due to local conditions, rapidly evolved into H. erectus, but other populations of H. habilis continued to exist contemporaneously for a long time). However, if there were in fact habitats for H. habilis to survive so long, it weakens the argument for rapid speciation into H. erectus. Again, this is not a definitive argument against the descent of H. erectus from H. habilis; most anthropologists do in fact believe that H. erectus is descended from H. habilis. It’s just one of those complications that needs to be better understood, and it increases the complexity of the landscape so far as different hominid species are concerned, in which humans involved.

Another point relevant to this discussion: H. habilis had a cranial capacity about half that of modern man, but much larger than australopithecines. Typical numbers are about 650-700 cc for adults, and the low end is about 510 cc. A. sediba has a cranial capacity of about 430 cc, which puts it below the range for H. habilis. This was one of the reasons why the authors preferred to classify the new fossils as australopithecine, rather than human (in anthropology, “human” typically refers to members of the genus Homo).

So what do these fossils say about human evolution? The answer is not clear, but several possibilities can be raised:

A. sediba is the direct ancestor of humans. This seems to be one of the possibilities that the authors lean towards, though by no means do they assert this as fact. To support this, they make certain claims and offer some reasoning. The claim is that previous to the discovery of these fossils, the best candidate for the ancestor of Homo would be A. africanus. Berger has made this claim before, though it is not widely accepted by other anthropologists. Since A. sediba seems to be intermediate between A. africanus and H. habilis in terms of physical characteristics, the argument could be made that the line of descent is A. africanus to A. sediba to H. habilis. The same theory of punctuated equilibrium could be used to explain the persistence of A. sediba to 1.8 million years ago, even though H. habilis appeared 2.3 million years ago. The chronology would then make sense: A. africanus (3.0 to 2.4 million years ago), A. sediba (? to 1.8 million years ago), and H. habilis (2.3 to 1.4 million years ago). This would mean that A. sediba originated somewhere between 2.4 to 2.3 million years ago, which is quite possible, though of course, the only specimens we have are these two fossils dated about 1.8 million years old.
A. sediba is a cousin instead of an ancestor. In this scenario, both A. sediba and H. habilis shared a common ancestor (some other species of Australopithecus). Similarities between A. sediba and H. habilis (such as the more human-like pelvis and skull) could be explained by either positing a more human-like australopithecine ancestor, which is yet to be discovered, or by convergence. After all, the climate and vegetation were changing, grasslands were becoming more common, and these changes might very well have affected two related species which shared the same habitat.
A. sediba is really not an australopithecine, but some ancestral species of Homo. In favor of this theory are a few things – the relatively young age (we know that H. habilis and probably H. erectus were already around at the time of these fossils), the previously mentioned wide variation in H. habilis specimens (which makes it more acceptable to think that this is just yet another variant), and the many human-like characteristics of these new fossils. Against that is the fact that the cranial capacity is smaller than we had previously accepted as the lower limit for Homo, and that the skeleton retains more primitive characteristics than are seen in Homo.

So at this point, it’s hard to say what the true situation is. If we classify these fossils as Homo, it could easily start a debate over whether earlier fossils are correctly classified. As I mentioned earlier, some of the older H. habilis fossils are quite fragmentary, and there have been arguments made in the past that some of them should really be considered australopithecines.

One problem in anthropology is that because of the scarcity of fossils, a lot of classifications are based on “type specimens” rather than any solid statistics. There is a large range of variability in any population (consider humans today, for example). In the absence of a sufficient number of fossils to quantify the extent of variability, anthropologists pick certain fossils with well-defined characteristics as “type specimens”, or “typical” of a certain species. Then when new fossils are found, their classification becomes a matter of relating them to known type specimens, setting up a chain of inferences. If you knock out a link in that chain (for example, declaring some early H. habilis specimen to be australopithecine instead), then there is a cascading effect on the classification of many other specimens, which were in part classified based on some similarity to these fossils.

In short, if we classify the new fossils as yet another variant of H. habilis, we will need to do some rethinking about other early specimens of H. habilis. Rethinking is always good, so this is not a problem. In fact, I am sure that right now there are many anthropologists busily thinking and writing away on just such issues.

Better answers will have to await more fossils. In the meantime, we have added to the richness and complexity of human evolution, and specifically to the period around 1.8 to 2.0 million years ago, which happens to be relatively fossil-scarce. We now have yet another species wandering around Africa at this time period, which is a critical period for the emergence of H. erectus, and the branch of the evolutionary tree leading to us.

EDIT [4/10/2010]: Scientific American has a story up quoting Donald Johanson (the discoverer of Lucy), in which he opines that (1) these fossils have been misclassified as Australopithecus, they are really a new species of Homo, and (2) he thinks it unlikely that this species descended from Australopithecus africanus.

The Neanderthal Predation Theory

Admin — Tue, 16 Feb 2010 10:59:46 +0000

I happened across this site, which belongs to Danny Vendramini, a TV producer and scriptwriter, with an interest in evolutionary biology.

Neanderthal face reconstructed by Vendramini, Copyright themandus.org

He has written a book called “Them and Us”, in which he propounds the hypothesis that Neanderthals were:

Very different looking from most modern representations – much uglier, hairier, and far less human-like.
That they were brutal, intelligent, tool-using predators, who preyed upon modern man in the areas where they came in contact, specifically, the Levant.
That being the prey of Neanderthals was the most important factor in human evolution, and that it was responsible for the flowering of art and sculpture, the technological innovations in the tool making industry, perhaps even the flowering of language – all of which happened around 40,000 to 50,000 years ago.
And not only that, it was responsible for the evolution of the human body type, including features that distinguish us from other apes, such as decreased hairiness, the development of a prominent and protruding nose, different body posture and gait, etc.
Finally, he lists a whole range of human behavioral traits, such as preference for symmetrical faces, fear of the dark, abominable snowman myths across various cultures, etc. as some sort of racial memory of Neanderthals, whom we fear and despise, because they preyed upon us.

Now at first read, this appears to be the work of a misguided though enthusiastic kook. He seems to have no formal qualifications in biology or paleo-anthropology, and is self-taught. He makes the first few chapters of his book available online, and from a quick read, he seems very dismissive of arguments that run counter to his thesis, for example, the loss of body hair in Homo sapiens. He mentions other theories, such as the thermoregulation during the transition from forest living to life on the savannah, but he dismisses them so hastily that it looks like he doesn’t really understand them all too well. Some of the examples he gives (such as big cats are predators, and some of them live in hot climates, why didn’t they lose their hair?) have reasonable answers in the literature, but he makes no mention of them. Instead, he pushes his theory, that we lost body hair because of sexual selection – we didn’t want to look like those ugly, murderous Neanderthals – it became a taboo to look like them.

Profile reconstruction of Neanderthal face, Copyright themandus.org.

Superficially, some of this may make sense. We certainly can’t rule out the role of sexual selection in the loss of body hair. But making the jump from “might be possible in a mundane way” to “it was a response to Neanderthal predation” is a very long stretch. He does this in many, many different areas, not just body hair.

Now I understand that he offers this as a hypothesis. He is not saying this is how it happened, just that this is how it might have happened. Which is fine, but the supporting evidence is very thin. Further, in his enthusiasm to bring in every possible argument to bear, he adds so much speculative and flimsy stuff that it makes it seem like he can’t distinguish between science and fantasy. To name a few, he finds some supposedly “universal” human traits such as xenophobia, preference for bathing and cleanliness, loyalty to the group, self-sacrifice, patriarchy, aggression, and many more, and ties them all into some imagined “prey psychology”, which developed as a result of humans being the victims of Neanderthals.

To be fair, he is not alone in this. Many so called “evolutionary psychologists”, or evolutionary biologists in general, make sweeping generalizations and assumptions, based on the flimsiest evidence. To me, this is an example of science turning into social narrative, the trivialization of science. You don’t need rigor and reasoning based on solid evidence, you don’t need to be cautious, to make no claim beyond the evidence – all you need to do is to tell a good story, preferably sensational enough to get picked up by the popular press, and give you your 15 minutes of fame.

Neanderthal with spear, Copyright themandus.org.

Part of it is the problem of generalists versus specialists. Evolutionary biologists or evolutionary psychologists (*shudder*) are generalists, tying together a lot of details from anthropology, genetics, sociology, psychology, etc. to make some broad claim. But in doing so, they often lack the specialized knowledge of each individual field – they lack sufficient knowledge to not over-generalize, and sometimes end up making silly blunders. They tend to trivialize and gloss over problems that are ambiguous and not resolved, picking the interpretation that favors their own theory, often not realizing that the foundation is very shaky.

And then there are those who disconnect with reality altogether, like Vendramini, when he goes off about connecting “fear of the dark” to nocturnal predation by Neanderthals or similar arguments. The pity is that he doesn’t seem to realize what he’s doing. In trying to add weight to his arguments, he is throwing in every last thing he can think of. And so he’s mixing in things that have some weight and credibility (like, we don’t really know exactly what Neanderthals looked like, perhaps they were more ape like than modern representations; or we don’t know exactly what human-Neanderthal interactions were like, there may well have been violence), with things that are utter nonsense, such as fear of the dark. So the good stuff gets mixed with the bad, and taints everything as trash. Further, it creates a bad impression of the writer, in that he doesn’t seem to be able to distinguish science from fantasy.

To top it all, he really appears serious about this airy-fairy stuff. He has another theory (and another whole website devoted to it), which propounds something he calls “teem theory”. In simple terms, the theory is that nasty stuff that happens to us and creates powerful negative impressions gets imprinted on non-coding regions of our DNA, and thus becomes heritable to future generations. This is what he uses to explain things like fear of the dark, xenophobia, etc. – that these bad experiences with homicidal Neanderthals became imprinted on our DNA, and continues to manifest in modern behavior.

That would be a whole other discussion and a whole other blurb on this blog, so I don’t want to get into it at this time. Briefly, he looks at instinctive behavior of a certain kind, such as certain animals instinctively recognizing their predators and avoiding them, concludes that such behavior must be coded into the DNA, since it’s untaught and not learned, therefore DNA must provide a mechanism for coding our fears. Such ideas ignore a whole realm of evidence, that a huge range of predator-avoidance behaviors are in fact learned, and that interpreting specific instances where they don’t appear to be learned is over-generalizing. Yes, there are instincts that are heritable, but the actual mechanism of how they work, what exactly is coded in the DNA, are very much unknown. Making it out to be something as specific as xenophobia is very imaginative, but poor science.

Neanderthal, hunting. Copyright themandus.org.

I see evolutionary biologists make similarly specific claims, that generosity and altruism are hard coded in our genes – all sorts of stuff like that. I consider it all very unlikely, an over-specification of something much broader. Perhaps what we are inclined for is social cohesiveness, being social animals, and specific instances of it are just a manifestation, they are not individually hard coded. It’s possible to take a population of rats, breed for either aggressiveness or docility, and in a very few generations end up with two distinct populations that are behaviorally very different in that respect. It’s been done. It doesn’t show anything very specific, other than that “fight” responses and aggression are more marked in one population than another, perhaps through some simple hormonal trigger. Going from that to very specific theories about brain centers dealing with aggression, or “cooperation” or something similar is not warranted by the evidence.

While I find his theory not convincing, it did make me wonder about a few things. What exactly do we know about how Neanderthals looked like? Forensic recreations based on bones have to be somewhat an exercise in guesswork, on prior knowledge. I agree with his point that they are not at all comparable to forensic recreations of humans. After all, we have a huge body of knowledge of what humans are supposed to look like, so our guesses are founded in a great deal of prior information. We don’t have a similar body of knowledge of what Neanderthals looked like, so our reconstructions may err on side of making them look too human (or conversely, less human) than they really were.

We have no casts of their soft tissues. We don’t know how hairy they were. We don’t know how much their noses protruded. We don’t know how big their eyes were, how erect their spines, how prominent their musculature. For all of these things, we make educated guesses, but some guesses are more educated than others. For example, the musculature is hinted at by the shape of the bones, the sites of attachment of various muscles to the bones. So this kind of guess can be trusted to a greater extent than say, the guess about how hairy they were, or what their skin was like, or how symmetrical their faces were.

So our picture can’t be very precise, there is some range of possibilities, within the constraints set by the bones. Just how wide that range is, I don’t know, and I wonder if they could have looked like the pictures on his web site. I don’t personally know of any physical evidence that goes against his reconstruction. Perhaps some more knowledgeable people can add to this. But it occurs to me that if Neanderthals looked sufficiently ape-ish, sufficiently non-human, it would explain why we find no evidence of human-Neanderthal interbreeding in the genomes. It would discourage (though not necessarily prevent) the two species from interbreeding.

I look forward to more information which should become available as the Neanderthal genome is fully sequenced and annotated.

Cooking and Evolution

Admin — Sun, 20 Sep 2009 05:01:48 +0000

This line of thought was provoked by an article I read talking about the importance of cooking food in the development of modern humans.

I’ve come across a number of articles that talk about the importance of a change in diet in human evolution. The theory is that human diet suddenly improved dramatically, and this marked increase in the availability of calories and nutrients was responsible for the growth of the brain. The improvement in diet is generally tied to either the switch from a primarily herbivorous diet to meat eating, and/or to cooking.

Both make sense in terms of calories and nutrients. Meat is certainly a more densely packed source of nutrients than plants. And cooking increases the bioavailability of nutrients, as it breaks up cell walls and structures that hinder our digestive enzymes from reaching the goodies inside cells.

Of course, this still leaves us without an actual mechanism. Evolution requires heritable changes in the genome. These happen largely by accident, though their selection depends upon what is advantageous to survival and reproduction. At this point, we don’t know very well exactly which genes are responsible for the differences in our brains, say compared to chimpanzees. We don’t know when these changes first appeared. We don’t know what connection they have to an improved diet.

So one part of evolution, that which is related to the genomic changes responsible for our large brains, is mostly unknown to us. Therefore, I think that ideas such as the change-in-diet leading to big brains scenario, tend to ignore the unknowns and focus only on the natural selection side of evolution. They make certain assumptions, for example, that a large brain will be selected, because it enhances survival and the chance to reproduce. This can be somewhat justified if one thinks about it (large brains, specially the growth of the forebrain is what allows us to make long range plans, analyze complex problems, etc.), and also there is fossil evidence that shows that in fact it was selected. Then there is the assumption that a large brain requires a nutrient rich diet, which can also be justified on the basis of the caloric expenditure in maintaining a large brain. A commonly offered statistic is that for a person at rest, of the amount of energy required to stay alive, the brain uses 20%, or 1/5th. The brain is obviously much less than a fifth of the body in terms of mass, yet it uses an extraordinary amount of energy, in proportion. If you keep the total mass of an organism constant, but increase the size of the brain in proportion to the rest of its body, then such an organism will require a more nutrient rich diet. In effect, you have increased its energy requirements, but have not given it bigger jaws to chew food, a bigger gut to digest it, bigger claws to hunt with, etc.

In fact, both anatomy and the fossil record show that humans became less capable of acquiring food as their brains grew, if we look solely at such biological markers such as tooth/jaw size. Homo erectus had smaller jaws than his ancestors, which would have made it harder for him to grind foods down and extract the most energy from them. Our gut became smaller, and less capable of extracting energy from plants. Our muscles became weaker, less capable of overpowering other animals through brute strength alone.
One would think that the timing of these changes would have some correlation with our behavior or change in diet, or the control of fire (for cooking). Unfortunately, the timing is much harder to pin down. No one really knows when humans first learned to control fire. Homo erectus, with his small jaws, evolved 2 million years ago, but the evidence for the widespread use of fire by humans at this time is scanty at best. Most anthropologists don’t believe that fire was used by humans this early, at least, not in any regular, controlled manner, such as would be needed for cooking. Soft tissues don’t fossilize well, so while we can study humans and chimps today and recognize that the chimp gut is much more suited for eating raw plant material than the human gut, we don’t really know when we evolved our more carnivorous digestive systems.

This leaves a chicken versus egg conundrum. Which came first, the big brain or the adaptations to the big brain lifestyle? Which was responsible for the other? This may be a silly question on the face of it, because obviously one is useless without the other. What’s the point of having a modern jaw or gut if you don’t also have the bigger brains that give you the means for filling that gut with food? On the other hand, how do you sustain that brain and give it energy without eating a more nutrient-rich diet?

So it seems that speaking in terms of absolute causality, one thing causing the other is somewhat simplistic. They probably both happened together, one reinforcing the other, and happened gradually. We didn’t go suddenly from a chimp-sized brain to a human-sized one, as we know from the fossil record. There are many intermediate stages of the brain growing progressively larger. The change in diet, therefore, and the behavioral changes accompanying both the change in diet and the larger brain, must have happened concomitantly.

It’s interesting at this point to bring in the factor we’ve ignored all along – that there must be genomic changes that produce all the anatomical differences – jaws, teeth, gut and brains. These genomic changes also need to be accounted for, and tied into the selection mechanism. A high nutrient diet is obviously not enough; otherwise large cats such as lions and tigers would be smarter than us. They might not cook, but they eat enough high nutrient food to be able to support bigger brains. They have evolved as long as us, why didn’t they learn to cook, why didn’t they evolve bigger brains?

This brings us back to selection, and fuzzier areas of anthropology such as social behavior and interactions, etc. We have bred dogs for a few thousand years, for example, and we have breeds of dogs today that look very different from each other. Not only is there is a difference in size and color of the fur, but there are also differences in the brain. Some breeds of dogs are smarter than others. We did this by a fairly simple process of selection – pick dogs that have the traits you want, breed them to produce a new generation, keep selecting for the desirable traits and reinforcing them through successive generations. Even with no knowledge of DNA or even Mendellian genetics, our ancestors were able to do this for dogs. We have also bred cows, pigs, goats, sheep, etc. – the modern domesticated forms of which are quite different from their wild ancestors. Not to mention the similar and parallel process of breeding food plants.

So even without postulating major and sudden changes in the genome, those which suddenly introduced a “game changer” mutation so far as the brain was concerned, it’s possible to see that humans could have become progressively smarter simply if the natural variation in smartness among a population was selectively reinforced over generations, the same way we breed dogs. Of course, this doesn’t mean that you can breed dogs to a human level of intelligence, there may well be certain required mutations, and these have to happen first. You can’t select for what doesn’t exist. But at a point where we don’t fully understand the nature of these key mutations, we can’t really talk about how essential they were. Perhaps they could happen in other species too. Perhaps there are a dozen different ways to get the same result, and if mutation “A” doesn’t happen, mutation “X” can provide the similar benefits. I’d rather not speculate about this until we have more information to speculate with.

So I think such articles (as the one referenced above, which talks about the relation of diet to human evolution) speculate about the remainder of the problem, the mutually reinforcing effect of the selection of traits which are part of the natural variability of a population, and the behavioral consequences of selecting such traits. You set a species on a certain path, on which a greater reliance on the brain cuts out some options while expanding others, and the options that are promoted require even greater brain power to work well. It’s interesting to speculate what put us on this path, why we seem to be the only species on it. What set of circumstances came together at the right time for this to happen. The drying climate and spread of grasslands, the change from an arboreal to a savannah type lifestyle, the appearance of bipedality at this critical juncture when these big new ecological niches suddenly opened up, the development of more and more hand flexibility with a greater range of movement in the opposable thumb (compared to other primates), the social interactions, etc. There were so many changes happening at roughly the same time to the same species, somewhere this set us off on a path to bigger brains.

The article that set me off on this line of thought, of course, talks about something narrower. It talks about the relationship of cooking to gender roles, the development of the male-female bond, which is marriage today. This seems less an evolutionary question than an anthropological one. The evolutionary part is the importance of cooked food in the development of our brains, which I have speculated about. The anthropology part is relating this importance to something else, namely male-female pairing. I am not qualified to speculate about the anecdotal evidence offered about some primitive societies where food is more important than marital fidelity. Nor do I have any evidence that women tended the home fires, though it seems likely if men were the hunters and spent less time at the home camp. This seems to be supported by fossil evidence, such as hunting related injuries, as well as by anthropological evidence. You can speculate that the importance of cooked food was critical enough to shape our behavior patterns in other ways, such as pair-bonding between males and females. But just because a theory seems to make sense doesn’t mean it’s true, so I guess we’ll need to see some more physical evidence before placing much value on it.

10,000 BC

Admin — Mon, 04 Aug 2008 22:00:45 +0000

I saw a re-run of the History Channel show Journey to 10,000 BC recently. My expectations from the History Channel continue to sink as they produce low quality shows full of factual errors and outright speculation presented as fact. They have turned into the Pseudoscience Channel.

Despite the broad sweep implied by the title “10,000 BC”, the show was limited to the North American continent, completely ignoring interesting events such as the beginning of agriculture, the domestication of animals, and the first monumental stone architecture, that were happening elsewhere in the world.

The show focused on the human occupation of the North American continent. It mentioned the prevailing theory that the paleo-Indians were of Beringian origin, who migrated from Asia across a land passage over the Bering Strait, which existed at the time due to lower sea levels. The Beringian people were of Siberian stock, but the show inexplicably chose Caucasian-looking actors to portray them. This discrepancy was later cleared up when they introduced the Solutrean Hypothesis, advocated by a number of people, including Dennis Stanford of the Smithsonian Institute.

The Solutrean Hypothesis proposes that the Clovis Point Culture was of European origin, specifically, an offshoot of the Solutrean Culture in Eastern France and Spain. The Solutrean industry is characterized by pressure-flaked bifacial stone points, which appear to resemble stone points found in ancient paleo-Indian sites such as Cactus Hill in Virginia, and the later Clovis Points. The idea is that Solutrean people moved across the Atlantic to the east coast of the North American continent, across a northern passage that consisted of large masses of packed ice interspersed between land masses (Iceland, Greenland). These people “followed the seal herds”, using animal skin boats to cross the stretches of water between land masses and ice packs, and eventually made their way into the Americas. The archeological finds at Cactus Hill appear to pre-date the Clovis Culture, and are inferred to be the remains of the early settlements of these Solutrean people from Europe. Sometime around 13,500 years ago, these people developed the fluted Clovis Point (an elongated Solutrean-like stone tool, with fluting at the base to allow it to better fit a spear haft), and the Clovis Culture spread across the continent.

Solutrean, Cactus Hill and Clovis Points

To support this theory, the show pointed out that most Clovis sites have been found in the Eastern US, indicating that the Clovis culture may have spread from east to west, which would be contrary to a west-to-east migration of people who had arrived via the Bering Strait and the Pacific coast.

Although the show mentioned a couple of times that this theory was “controversial”, it failed to mention the large body of evidence against it, nor did it even attempt to offer equal time to any of a number of mainstream archeologists and anthropologists who oppose it. It continued to represent the paleo-Indians through Caucasian actors, going so far as to present a hypothetical confrontation between these Caucasians, and the Asian Siberian people who arrived through the Bering passage. The confrontation ends in a fight, with the implication being that the Asians possibly wiped out these early Europeans. There is a lot more about the end of the Clovis culture, with the concomitant disappearance of the native mega fauna with the climate cooling of the Younger Dryas, a hypothesis that this may have been caused or aided by an asteroid impact, etc.

While controversy sells, this account shortchanges the truth in many ways. The Solutrean hypothesis is not widely accepted, and is contradicted by several lines of evidence. Its support rests upon a similarity between the appearance of Solutrean and Cactus Hill / Clovis points. Such similarities may result in a number of ways. Tools develop to fulfill certain functions, and a bifacial pointed tool that can be attached to a wooden stick to form is spear is singularly handy for bringing down large game, which both the Solutreans and the Clovis Point people did. After all, there are only so many ways you can design a hammer, or a knife. If the tool is to be used for a particular purpose, its design will naturally lead to a form suitable to that function, whether done by Solutreans in France, or paleo-Indians in the Americas.

There are a number of unexplained factors to consider. How did these Solutrean people cross the Atlantic? Proponents of this hypothesis believe they used animal skin boats. No evidence of such a boat building Solutrean culture has ever been found, but the proponents claim it could easily have been lost, since you would expect to find its remains along coastal regions, which have long since been submerged as the ice melted. There is a distinct lack of other Solutrean features in the Clovis Point people, other than these bifacial stone points. There is an unexplained 2,000 – 3,000 year gap between the end of the Solutrean industry in Europe, and the emergence of Solutrean-type tools in the Americas. Where were these people then? Where is the evidence that they kept this industry alive in the meantime?

There is little evidence of any European inheritance dating to this period in modern native American populations. Earlier studies showed a significant prevalence of haplogroup X in the mitochondrial DNA of native Americans. Haplogroup X is found predominantly in west Asia and Europe. However, the latest research shows that all current native American populations are likely descended from a single group in Berengia, which took part in a series of migrations along the Pacific coastal route into the Americas, between 18,000 to 15,000 years ago. These are, in fact, the pre-Clovis people.

Haplogroups A–D are also frequent in Asia, suggesting a northeastern Asian origin of these lineages. However, the differential pattern of distribution and frequency of haplogroup X led some to suggest that it may represent an independent migration to the Americas. Here we show, by using 86 complete mitochondrial genomes, that all Native American haplogroups, including haplogroup X, were part of a single founding population, thereby refuting multiple migration models.

- Fagundis, et al. Amer. J. Human Genetics, 82: 1-10, March 2008

None of this was mentioned in the documentary. Nor was there any mention of the range of pre-Clovis sites that have been found along the Pacific route (such as the 14,300 year old human coprolite found in a cave in Oregon, or the Monte Verde site in Chile, dated to 14,500 years old). The Monte Verde II site is the oldest reliably dated human settlement in the Americas, at least 1,000 years older than any other. If the paleo-Indians could reach and settle a point thousands of kilometers farther from their point of entry into the Americas than Cactus Hill, or the Clovis sites along the east coast, why could they not have reached the east coast sites, which are much closer? Just because we have found more Clovis sites along the east coast does not imply an eastern origin to the people. There is every reason to believe that there were pre-Clovis people scattered throughout the continent, and that these people could easily have been descendants of paleo-Indians from Berengia. Clovis point is simply a tool making industry, and it says little about the nature or origin of the people who developed it.

Presenting such a one-sided account of a controversial hypothesis which has found little acceptance in academia does a disservice to the audience. Most people who watch the History Channel are not experts in this field, and will tend to accept it at face value. When the bulk of the program consists of a couple of these controversial scientists presenting their theory, interspersed with shots of Caucasian actors stalking mammoths, the average viewer is left with the impression that this is in fact what happened.

The show had numerous other factual errors. Twice, the narrator claimed that the Columbian mammoth hunted by these Caucasians was the “largest land animal since the dinosaurs”. This is completely untrue. Apparently, they forgot the indricotheres. Even worse, they ignored other larger mammoths, such as the Imperial mammoth that lived right here in the Americas, or the even larger Sungari mammoth or Steppe mammoth from Siberia. Surely they could have avoided such mistakes if they had just run the script by even one expert. There were numerous instances of cheap shoddy work. The CG effects were horrible. The mammoths look like something out of a cheap computer game.

Having a low budget is not a crime, but distorting science to present controversial theories that are probably wrong as fact is unforgivable for a science program. It only supports my contention that the History channel is all about entertainment, and has little to do with facts.