Human Evolution
gregladen | February 12, 2009And hominids.
We know the fossil record underestimates diversity at least a little, and we know that forested environments in Africa tend to be underrepresented. Given this, the diversity of Miocene apes may have been rather impressive, because there is a fairly high diversity in what we can assume is a biased record.
But I'd like to make the argument from another angle, that of modern ecological analogues. Let us assume that the greater apparent diversity of apes in the middle and late Miocene compared today can be accurately translated as a modern reduction in ape diversity. Not…
edyong | February 11, 2009This is the sixth of eight posts on evolutionary research to celebrate Darwin's bicentennial.
Physically, we are incredibly different from our ape cousins but genetically, it's a different story. We famously share more than 98% of our DNA with chimpanzees, our closest living relatives. Our proteins are virtually identical and our chromosomes have more or less the same structure. At the level of the nucleotide (the "letters" that build strands of DNA), little has happened during ape evolution. These letters have been changing at a considerably slower rate than in our relatives than in other…
gregladen | February 4, 2009The complete genome of a Neanderthal dating to about 38,000 years ago has been sequenced by the team lead by Svante Paabo. The genome will be announced on Darwin's Birthay, Feb 12.
"We are working like crazy at the moment," says Pääbo, adding that his Max Planck colleague, computational biologist Richard Green, is coordinating the analysis of the genome's 3 billion base pairs.
Comparisons with the human genome may uncover evidence of interbreeding between Neanderthals and humans, the genomes of which overlap by more than 99%. They certainly had enough time for fraternization -- Homo…
gregladen | January 11, 2009One of the most interesting and exciting stories in science is that of the Younger Dryas. The Younger Dryas was a climate event that had important effects on human history, and that has been reasonably linked to some of our most important cultural changes, and ultimately some evolutionary changes as well. That is one reason why it is interesting. In addition, the Younger Dryas was a pretty big deal ... a climate change or something like a climate change that caused massive changes all around the earth, and fairly recently. But the cause of the Younger Dryas is at present unknown, although…
gregladen | December 13, 2008 What was Neanderthal-Modern Human interaction really like? Fifty four teeth (some of which are fragments) and nine other bones dating to about 40-43,000 years ago represent the "most recent, and largest, sample of southern Iberian late Neanderthals currently known."
These and some closely related remains may indicate that these Middle Paleolithic holdouts were kissing cousins of nearby anatomically modern humans. Or maybe not.
We know that Neanderthals occupied all of Europe for over 125 thousand years during a period known (from the artifacts) as the "Middle Paleolithic." During…
gregladen | December 5, 2008Allen's Rule. One of those things you learn in graduate school along with Bergmann's Rule and Cope's Rule. It is all about body size. Cope's Rule ... which is a rule of thumb and not an absolute ... says that over time the species in a given lineage tend to be larger and larger. Bergmann's Rule says that mammals get larger in colder environments. Allen's Rule has mammals getting rounder in colder climates, by decreasing length of appendages such as limbs, tails and ears.
All three rules seem to be exemplified in human evolution. Modern humans tend to be larger and rounder in cooler…
gregladen | October 24, 2008There is a new paper, just coming out in Proceedings of the National Academy of Sciences, that explores the idea that humans have undergone an increased rate of evolution over the last several tens of thousands of years.
By an increased rate of evolution, the authors mean an increased rate of adaptive change in the genome. By recent times, the authors mean various things, depending on which part of the analysis you examine, and depending on what is meant by "increased." ... In other words, the timing of an event that is not really an event (but rather a change in rate of something) is hard…
gregladen | October 22, 2008Homo floresiensis more widely known as the "Hobbit," may have had arms that were very different from those of modern humans. A paper in the current issue of the Journal of Human Evolution explores the anatomy of H. floresiensis. To explore this we first have to understand the concept of "Humeral torsion." Humeral torsion is the orientation of the humeral head relative to the mediolateral axis of the distal articular surface. Don't bother reading that sentence again, I'll explain it.The humerus is the upper arm bone, that runs between your shoulder and your elbow. The humeral head is the…
gregladen | October 21, 2008It has always been suggested, by a wide range of evidence, that australopiths in general, and robust australopiths in particular, have a higer degree of sexual dimorphism than chimps, and possibly, dimorphism in body size as high as one sees in any ape. Resent research on growth patterns, just published in Science, examines this.
In dimorphic primates, the larger size of the male is usually obtained by an extended period of growth of the males, so they essentially "grow past" the females. In addition, there are usually additional traits that the larger, adult males have that re not seen in…
gregladen | October 21, 2008
Every few years a paper comes out "explaining" short stature in one or more Pygmy groups. Most of the time the new work ads new information and new ideas but fails to be convincing. This is the case with the recent PNAS paper by Migliano et al.
From the abstract:
Explanations for the evolution of human pygmies continue to be a matter of controversy, recently fueled by the disagreements surrounding the interpretation of the fossil hominin Homo floresiensis. Traditional hypotheses assume that the small body size of human pygmies is an adaptation to special challenges, such as…
gregladen | October 18, 2008Or, to be less crude, did modern humans, having already evolved in Africa, interbreed with the local Europeans who were Neanderthals, and if so, did they produce fertile offspring ... and, did this happen in sufficient degree to have mattered at all to the genetics of later (but not necessarily living) people?
In my opinion, the answer is, of course they interbred. There are many reasons to believe this if almost no way to prove it. Indeed, the evidence of this interbreeding is virtually nil. With every additional test of the interbreeding hypothesis using DNA, the null hypothesis of no…
edyong | October 11, 2008
While philosophers and poets muse on the meaning of life, natural selection casts a dispassionate eye on the whole affair. From the viewpoint of evolution, there is only one thing that matters - that we survive long enough to pass our genes on to the next generation, as many times as possible. And from the viewpoint of evolution, we are not doing a very good job.
Birth rates in several countries around the world - the UK, Japan, China - are falling dramatically. Women are having fewer children and they are having them later, close to the end of their fertile period. But the fact that…
gregladen | October 7, 2008The Science Museum of Minnesota recently developed an exhibit called "Race: Are we so different?" This exhibit is now at the Cleveland Museum of Natural History, and will be in Cincinnati, Philadelphia, Los Angeles, St. Louis, New Orleans, Kalamazoo, Boston and Washington DC between now and June 2011.
If you get a chance, go see it.
In the meantime, a review of this exhibit has just been published in the current issue of Museum Anthropology, authored by Mischa Penn, Gil Tostevin, and yours truly, Greg Laden.
As one of the authors, it is obvious to me that this paper is brilliant! But I…
gregladen | September 29, 2008Human societies tend to be at least a little polygynous. This finding, recently reported in PLoS genetics, does not surprise us but is nonetheless important. This important in two ways: 1) This study uncovers numerical details of human genetic variation that are necessary to understand change across populations and over time; and 2) the variation across populations are interesting and, in fact, seem to conform to expectations (in a "we don't' really care about statistical significance" sort of way, for now) regarding human social organization.
Before examining the paper, we should…
gregladen | September 19, 2008 Gustavus The Nobel Conference at Gustavus Adolphus College, naturally.
Gustavus Adolphus was the king of Sweden and founder of the Swedish Empire from the age of seventeen until he his death at the age of 37, in 1632. He looked, as a testosterone-ridden teenager, at vast unconquered lands, at his large and experienced army, and noticing that he was in charge of everything, made a run at taking over the world. He left Sweden with his army and never looked back.
Meanwhile, well, a couple of centuries later, Alfred Nobel was busy inventing TNT and establishing the Nobel Prizes for…
edyong | September 4, 2008The image on the right is both beautiful and exciting. Let me explain why. It's the paw of an embryonic mouse and a team of geneticists have inserted a fragment of human DNA into its cells. The fragment contains an "enhancer" element, a short span of DNA that switches other genes on and off; in this case, they put the enhancer in control of a gene whose activity creates a blue chemical.
This particular enhancer is called HACNS1. Throughout the course of animal evolution, its sequence has gone relatively unchanged in almost all back-boned animals, but it has evolved rapidly in the human…
gregladen | August 14, 2008Stephen Jay Gould and David Pilbeam wrote a paper in 1974 that was shown ten years later to be so totally wrong in its conclusions that it has fallen into an obscurity not usually linked to either Gould or Pilbeam. However, they were actually right in ways that they could not have anticipated. And even if they were not right, this paper still has much to contribute, including the opening words of that publication in Science, which are very much worthy of consideration for many reasons:
It is no longer true that there are more practitioners than pieces. In fact, when I encountered this…
jlynch | July 26, 2008(This review appeared in the American Journal of Physical Anthropology in 2005)
As human beings, we like to tell stories--we are story-telling apes. As scientists, however, we tend not to see ourselves as telling stories for, we are led to believe, stories are mere fiction. Yet when faced with answering the question of why or how we became story-telling apes, we are often presented with a series of hypotheses with little empirical evidence to distinguish between them. In many ways, Wiktor Stoczkowski claims that it is because we are storytelling apes, and that because stories often represent…
jlynch | July 14, 2008
Very sad news for those of us who do physical anthropology. Charles ("Charlie") Lockwood (University College London) was killed today in a motorcycle accident in London. He is survived by his parents and sisters.
Charlie was a talented morphologist both in the sense of being a descriptive anatomist and quantitative biologist. I met him in the late 90's when he came to ASU's Institute of Origins for a post-doc after completing his PhD at the University of Witwatersrand. He, Bill Kimbel and I shared the pain of rejected NSF grant proposals before receiving NSF money to study the use of…