Is your Dad the descendent of a Neanderthal? Visit our PLoS website to find out more.
Recent evidence has shown that a small percentage of human DNA is Neanderthal. This Neanderthal DNA entered the human gene pool between 80,000 and 50,000 years ago.
While human DNA may contain traces of Neanderthal ancestors, mitochondrial DNA from Neanderthals has not been found in humans. Mitochondrial DNA comes uniquely from your mother. Is it plausible that male Neanderthals were able to mate with female humans, but that the reciprocal cross was unable to occur?
Analyses of the Y chromosome suggest that we share a common male ancestor 59,000 years ago. Could this male ancestor have possibly been Neanderthal?
If our common male ancestor is neanderthal, and considering that the Y chromosome is transmitted uniquely through the paternal line, could it mean that men are more closely related to Neanderthals than women? Have men and women truly come from two different species?
Visit the full post on our PLoS website for the full explanation of this intriguing hypothesis.
We are not our genes and they are not us. Knowing what copies of genes we carry can tell us a little about getting sick and losing our hair, and maybe even add insight into our ancestry. But that does not tell us about how and why we do the things that we do.
Steven Pinker, in his recent New York Times Magazine article My Genome, My Self, argues that genes do have great influence on our behavior. As an anthropologist, evolutionary theorist, and a researcher of human and other primate behavior I am here to tell you that he is overshooting the mark. Human behavior is simultaneously biology, culture, experience and more.
Natural selection, one of the main drivers in evolutionary change, works on the whole body and behavior complex, not on single genes or even the genome itself. It is the dynamic product of genes, organs, bodies, behaviors, ecologies, and societies that eventually affects evolutionary patterns in humans. No gene or even set of genes can be held in isolation of the systems in which they exist.
Since I’m in Dunedin, New Zealand, I thought I’d write on one of the University of Otago’s most neuroanthropological philosophers, Prof. James Flynn, and dive back into the maelstrom around average IQ scores in different social groups. Prof. Flynn famously pointed out to people outside the standardized testing industry that IQ tests had to be periodically recalibrated because average IQ scores in industrialized countries steadily inflated, suggesting either that people were growing smarter or something else was up with these tests.
Flynn gathered tests from Europe, North America and Asia, around thirty countries in all, and discovered that, for as far back as we had data in any case, average IQ test scores had risen about 3 points per decade and in some cases more. Only recently, in some Scandanavian countries, to the gains appear to be levelling off (see, for example, Sundet 2004; Teasdale and Owen 2005).
Ironically, in spite of the fact that children spend longer on average in school than in previous decades, the Flynn Effect does not show up on the parts of standardized tests that measure school-related subjects. That is, tests of vocabulary, arithmetic, or general knowledge (such as the sorts of facts one learns in school) have showed little increase, but scores have increased markedly on tests thought to measure ‘general intelligence’ (or ‘g’), such as Raven’s Progressive Matrices which require mental manipulation of objects, logical inference, or other abstract reasoning.
The Cognition and Culture website has posted a link to the new edition of the Philosophical Transactions of the Royal Society B on ‘cultural transmission and evolution of human behaviour.’ I wanted to comment on just one piece on embodied cognition and cultural evolution, by philosophers Michael Wheeler and Andy Clark (unfortunately, Philosophical Transactions B is behind a subscription wall, although there’s a one-page ‘free preview’ [ouch] here). The Cognition and Culture website has the table of contents posted here. I was vaguely familiar with Michael Wheeler’s work before this piece, but Andy Clark (it’s not much of a profile) has written some of the work that’s most influenced my thinking about the effects of varied skill acquisition on cognition, especially his remarkable book, Being There: Putting Brain, Body and World Together Again (Amazon listing).
A ream of Clark’s papers can be found here. A review of Michael Wheeler’s book, Reconstructing the cognitive world: The next step, written by Leslie Marsh can be downloaded here. We’ll come back to Andy Clark’s work again in later posts.
I must admit a certain morbid fascination with how one of my favorite streams of thought — embodied cognition — would fare combined with cultural evolution — an area of scholarship that, well, to put it nicely, is uneven (before you get all defensive, let me just stop you with one word: mimetics). It’s sort of like watching one of your good friends get hit on by a sleazy guy at a bar. She looks happy, but you’re sort of cringing at the chance that she might actually take him home. In spite of this instinctual cringe, this special edition of Philosophical Transactions has some really interesting work on cultural evolution, especially because many of the pieces focus tightly on the enormously problematic issue of cultural transmission.
The special explores epigenetics and the complex network of regulatory mechanisms that affect gene expression, including a nice little slideshow on Hox genes. We’ve explored the topic before here at Neuroanthropology (see Pharyngula on epigenetics) in part because a better understanding of the molecular mechanisms of organic development tends to undermine the overly simplistic notion that there are two forces shaping any organism — genes and environment or ‘nature’ and ‘nurture.’ With the epigenetic material, it’s painfully obvious that genes are not some kind of organic destiny writ in DNA, as some popular understandings tend to have it (and that popular understanding is often mobilized in simplistic accounts of subjects like behavioural genetics, as we will know).
We’ve already discussed some of the quirks about twins’ genes here (at Identical twins not… err… identical?), and there’s a nice example of genetically identical twin mice looking anything but identical (and having significant differences in health). The story, ‘A Tale of Two Mice,’ has a sobering subtext about the effects on gene expression of BPA (Bisphenol A), an organic chemical known to leach out of plastics (see Wikipedia for a brief overview of the issues). However, I’m still not convinced that calling this complex interaction ‘the epigenome’ or ‘the second genome’ is moving in the right direction. Even with this reservation, the visual aids for thinking about epigenetic processes are excellent.
Thanks to Dr. Jovan Maud (from Macquarie University and Culture Matters) for pointing this piece out to me. Unfortunately, I just gave my lecture on this stuff a week and a half ago — I’m afraid that I confused my audience a lot more than the people at Nova. It’s a nice site though for getting a bit of a feel for the sorts of factors that affect gene expression.
The brilliant graphic accompanied a reprint of Sean B. Carroll’s article, ‘The Origins of Form: Ancient genes, recycled and repurposed, control embryonic development in organisms of striking diversity,’ originally published in Natural History, November 2005. Carroll’s article can be accessed here, and it’s a great entry-level piece on hox genes and basic ‘evo-devo’ thought, but the author of Endless Forms Most Beautiful.
P. Z. Myers of Pharyngula, when he isn’t driving creationists into paroxysms, can write some great translations of biological concepts for the average reader. He does this in the post, Epigenetics, where he points out some of the problems with textbook definitions of the term. I really recommend checking this post out, but get a cup of coffee and a comfortable seat before you do — the post is not lite fare.
Epigenetics, although devilishly difficult, is absolutely essential for breaking with the common conception of DNA as ‘blueprint’ or marching orders for biological processes. In biological developmental processes, the expression of DNA is quite a bit more interesting than just ‘genes made it happen.’ Myers lays out a host of good examples, such as the variable degree to which histones permit or inhibit DNA transcription, the inactivation of parts of DNA when methylated, how chromosome geometric arrangement might affect gene expression, and other factors. He also discusses X chromosome inactivation in females (because they have two, one has to shut down), genomic imprinting on non-sex chromosomes (Myers discusses chromosome 15 and some of the disorders that can result), and disease changes in genetic expression (such as liver cirrhosis and retroviral insertions, which I touched on in an earlier posts on ‘identical’ twins).