Human Evolution
gregladen | January 4, 2010I had mentioned earlier that the volcanoes of the Virugna region in the Western Rift Valley (as well as other highland spots) have often been islands of rain forest separated from each other by different habitats, including grasslands and wooded savannas. this has produced an island effect that has been a laboratory for evolution, and it is likely that these forest islands (and others in the greater region of east Central Africa and western East Africa) have been the loci of evolution of many endemic species. (See Island Africa: The Evolution of Africa's Rare Animals and Plants by Kingdon…
sporte | January 4, 2010An NSF post on Twitter this morning described an interesting study from the University of Pennsylanvia and Cornell University, that found that some people who call themselves "African Americans" may only be 1% West African, according to their DNA.
The University of Pennsylvania press release contains other interesting findings as well. 365 individuals were studied and 300,000 genetic markers were examined.
Some of the findings were:
If you're African American, the genes most likely to have an African origin are those on your X chromosome. The article didn't mention it, but I would guess…
razib | December 21, 2009Spatial Organization of Hominin Activities at Gesher Benot Ya'aqov, Israel:
The spatial designation of discrete areas for different activities reflects formalized conceptualization of a living space. The results of spatial analyses of a Middle Pleistocene Acheulian archaeological horizon (about 750,000 years ago) at Gesher Benot Ya'aqov, Israel, indicate that hominins differentiated their activities (stone knapping, tool use, floral and faunal processing and consumption) across space. These were organized in two main areas, including multiple activities around a hearth. The diversity of human…
razib | November 30, 2009Wet phases in the Sahara/Sahel region and human migration patterns in North Africa:
The carbon isotopic composition of individual plant leaf waxes (a proxy for C3 vs. C4 vegetation) in a marine sediment core collected from beneath the plume of Sahara-derived dust in northwest Africa reveals three periods during the past 192,000 years when the central Sahara/Sahel contained C3 plants (likely trees), indicating substantially wetter conditions than at present. Our data suggest that variability in the strength of Atlantic meridional overturning circulation (AMOC) is a main control on vegetation…
gregladen | November 17, 2009The first part of this documentary, including the preface and the first several minutes of the main body of the work, should be deleted. The writers and producers who put that part together should be captured, gutted, eviscerated, and their dried and salted remains staked to the front entrance of the Public Broadcasting System as a reminder for other writers and producers. Why? Here's why:
What was said was pure teleology. At some point, sixty million years ago, the path that human evolution would follow was set. Some of the ancestral forms stayed on the path to us, others did not and…
emjohnson | November 17, 2009See thro' this air, this ocean, and this earth
All matter quick, and bursting into birth:
Above, how high progressive life may go!
Around, how wide! how deep extend below!
Vast chain of being! which from God began;
Natures ethereal, human, angel, man,
Beast, bird, fish, insect, who no eye can see,
No glass can reach; from infinite to thee;
From thee to nothing.--On superior powers
Were we to press, inferior might on ours;
Or in the full creation leave a void,
Where, one step broken, the great scale's destroyed:
From Nature's chain whatever link you like,
Tenth, or ten thousandth, breaks the…
edyong | November 16, 2009At first glance, the African elephant doesn't look like it has much in common with us humans. We support around 70-80 kg of weight on two legs, while it carries around four to six tonnes on four. We grasp objects with opposable thumbs, while it uses its trunk. We need axes and chainsaws to knock down a tree, but it can just use its head. Yet among these differences, there is common ground. We're both long-lived animals with rich social lives. And we have very, very large brains (well, mostly).
But all that intelligence doesn't come cheaply. Large brains are gas-guzzling organs and they need…
gregladen | November 10, 2009I watched a pre-release copy of tonights show, the second of three episodes, last week, and I have some comments to make about it. The short version: Do watch it! Then report back here and tell us what you thought.
I've seen every single human evolution documentary ever made, and some of them I know by heart, having used them in teaching. The present work, a three hour updated look at human evolution, satisfies most of my requirements for use in a classroom setting or for general dissemination of knowledge about human evolution.
The second episode focuses on Homo erectus and related forms…
razib | October 26, 2009Neanderthals 'had sex' with modern man:
Professor Svante Paabo, director of genetics at the renowned Max Planck Institute for Evolutionary Anthropology in Leipzig, will shortly publish his analysis of the entire Neanderthal genome, using DNA retrieved from fossils. He aims to compare it with the genomes of modern humans and chimpanzees to work out the ancestry of all three species.
...
Paabo recently told a conference at the Cold Spring Harbor Laboratory near New York that he was now sure the two species had had sex - but a question remained about how "productive" it had been.
"What I'm…
gregladen | October 22, 2009He talks about his book, The Greatest Show on Earth: The Evidence for Evolution. The interviewer is not my favorite interviewer. A public radio interviewer should not even be asking questions about religion and creationism unless doing a story that is explicitly on fringe beliefs. She digs in just after 16 minutes with the meany atheist thing. But here you have it:
edyong | October 21, 2009Cast your mind back to June, when a stunning fossil animal called Darwinius (alternatively Ida or "The Link") was unveiled to the world to tremendous pomp and circumstance. Hyperbolic ads declared the day of Ida's discovery as the most important for 47 million years. A press release promised that she would "change everything", headlines proclaimed her a "missing link in evolution" and the scientists behind the discovery billed her as "the closest thing we can get to a direct ancestor".
And according to a new study, none of that is true. Mere months later, Erik Seiffert from Stony Brook…
emjohnson | October 18, 2009Grand evolutionary dramas about human origins capture our imagination and the stories provide context as to how we view ourselves. They are the scientific version of creation myths. However, unlike Adam and Eve being fashioned in the garden or humanity being vomited up by the giant Mbombo (as the Bakuba people of Congo believed), scientific origin stories are rigorously critiqued based on the best available evidence.
Friedrich Engels, a sociologist and future collaborator with Karl Marx, wrote one of the earliest scientific human origin tales in 1876. In his essay "The Part Played by…
emjohnson | October 18, 2009Classical literature has judged Helen of Troy harshly. Because she chose Paris after having children with Menelaus, her chroniclers condemn her for the destruction of a great society. In Homer's Odyssey the bard writes:
Helen would never have yielded herself to a man from a foreign country, if she had known that the sons of Achaeans would come after her and bring her back. Heaven put it in her heart to do wrong, and she gave no thought to that sin, which has been the source of all our sorrows.
This has been the tradition in Western society. An open female sexuality has been viewed as…
emjohnson | October 16, 2009Three products that profit on male insecurities (Enzyte, Viagra and Tiger Penis Wine)
Note: the third image is from a campaign to encourage people to stop, not an actual ad.
In my earlier posts I explored why women experience menopause and discussed the Grandmother Hypothesis as a leading explanation. There is accumulating evidence that suggests reproductive senescence in women is an adaptation promoting inclusive fitness. However, there are many claims that menopause also occurs in men. There's even a fancy name for it: andropause.
A quick Google search reveals an onslaught of online "…
emjohnson | October 15, 2009There may need to be a significant revision in the recent description of one of humanity's oldest ancestors. Ardipithecus ramidus (or "Ardi" for short), the 4.4 million year old hominid fossil discovery, has been a godsend to paleoanthropologists (pun intended). But one of the key researchers has made what could be a serious error in his interpretation.
Christopher Ryan, who writes for Psychology Today at his blog Sex at Dawn (also the title of his forthcoming book) has discovered evidence that could undermine Owen Lovejoy's argument about human sexual evolution ever since Ardi:
In a…
razib | October 14, 2009Reading the papers on Ardipithecus ramidus which just came out in Science one of the take-home points that jumps out at me is that extant apes may be very misleading analogs to extinct hominins. Here is Owen Lovejoy:
In retrospect, clues to this vast divide between the evolutionary trajectories of African apes and hominids have always been present. Apes are largely inept at walking upright. They exhibit reproductive behavior and anatomy profoundly unlike those of humans. African ape males have retained (or evolved, see below) a massive SCC and exhibit little or no direct investment in their…
emjohnson | October 13, 2009In my earlier post I discussed the "Grandmother Hypothesis" as an explanation for human reproductive senescence, or menopause. A problem arises in understanding why women forgo one-third (and sometimes as much as one-half) of their reproductive lives, a condition unique in the natural world. Could this just be a neutral mutation, an artifact of longer human lives, or might it be a product of natural selection? If the latter, what selection pressure(s) could result in this unique human adaptation? The grandmother hypothesis posits that women who stopped ovulating in their golden years were…
emjohnson | October 12, 2009Whether they're referred to as hot flashes, power surges or personal summers, the experience of menopause is not fun. But could it be the result of human evolution?
One of the most fascinating areas of research in evolutionary studies is the question of reproductive senescence. Why do women go through menopause? Chimpanzees and bonobos, our closest evolutionary relatives who we share 99% of our DNA with, are reproductive throughout their lifespans but human women can spend the last third of their lives infertile. Why?
Biologist Virpi Lummaa, whose recent work on evolutionary theory and birth…
emjohnson | October 10, 2009
In the classic film Casablanca, the drama hinges on Ilsa's choice between two men: her kind and supportive husband or her rugged and passionate ex-lover. In a moment of abandon, Ilsa returns to her lover's arms only to later change her mind and choose the more stable life she would have with her long-term partner. But what if something as simple as a pill had caused Ilsa to feel differently and make the opposite choice?
In a new paper in the journal Trends in Ecology and Evolution biologists Alexandra Alvergne and Virpi Lummaa at the University of Sheffield in England raise the possibility…
emjohnson | September 24, 2009Seed magazine has just posted my review of Frans de Waal's The Age of Empathy: Nature's Lessons for a Kinder Society. I wanted to use this opportunity to thank Nikki, Evan, Bora and everyone else that helped in developing this piece. For posts on related topics please see Misunderstanding Dawkins, The Sacrifice of Admetus, Bonobos "Red in Tooth and Claw", The Evolution of Morality and Laboratory Evidence for the Breakdown of the Selfish Gene.
In a fitting metaphor, the most recent experiment with social darwinism resulted in mass extinction. Former Enron CEO Jeffrey Skilling claimed he was…