Wednesday, July 27, 2011

Speculations About Fire, Liquid Hot Magma, and Human Evolution

DISCLAIMER: this post is just for fun and does not report on mainstream paleoanthropological research. The title of the paper in the Journal of Fire Ecology is actually "Speculations About the Effects of Fire and Lava Flows on Human Evolution".  The author comes right out and says that
this paper is not a scientific presentation of hypotheses that have been extensively tested in the field. Rather, it is a playful exercise in speculation and even 'just so stories' about human evolution and fire.
And the author Michael Medler certainly does speculate.  He starts by making the observation that hominins  (east African ones at least) evolved in a region characterized by very active volcanism (indisputable). Perhaps then, he goes on, fire has shaped human adaptations over millions of years.  This is not totally outside the realm of what some actual anthropologists have said (e.g Wrangham, 2009)....more or less that fire for cooking food and warmth was really important late in human evolution as hominins spread out of the tropics.

Tuesday, July 26, 2011

Homo erectus (or georgicus) in the Caucasus at 1.85 Ma-icus

Ferring et. al 2011. PNAS 108:10432-10436. Figure 3
Ferring et al. describe the result of an archaeological test trench at Dmanisi in this PNAS article. They found a pretty standard Mode I lithic assemblage (full disclosure: I am not at all a lithics person). What is remarkable is the fact that the site appears to have been occupied as early as 1.85Ma.  This pushes back the dates for occupation of Eurasia by an erectus-like hominin far enough to rival (and even be a teensy bit older) than the earliest dates for H. erectus/ergaster in Africa. Very cool! The authors go as far as to suggest that H. erectus originated in Eurasia instead of Africa.  Could be, but in my opinion we will need lots more even earlier fossils from Eurasia to support that hypothesis.

Monday, July 25, 2011

Paranthropus boisei: Cow-Man of the Pleistocene?

The elusive cow-man
Lots of anthropological research focuses on figuring out what our ancestors ate. One long-standing question concerns the diet of robust australopithicines, a group of three species of early hominin that most researchers place together in the genus Paranthropus. These three species share a suite of adaptations of the teeth, jaws and cranium which all relate to extremely powerful chewing. The consensus among researchers has been that Paranthropus species ate a diet of hard objects (e.g. nuts or hard fruits), or perhaps a difficult-to-process diet of tubers and other undergrouund plant storage organs.  

A new carbon isotope study reported in this article in PNAS by Cerling and colleagues argues that P. boisei subsisted on C4 vegetation like grass and sedges, not on hard objects (hence the cow photo). This is consistent a previous study of dental microwear by Ungar et al. of which found no evidence for hard object feeding in P. boisei.  This result is surprising, as several dental microwear studies of the southern African robust hominin P. robustus are consistent with hard object feeding in this species, and carbon isotopes for robustus show much more C3 plant use (C3 vegetation comes from bushes and trees, including fruit). Thus, it appears that there may have been considerable dietary diversity within this genus, with P. boisei having diverged from a more "traditional" primate diet to focus on grazing. 

Sunday, July 24, 2011

Neanderthal/Human Hanky Panky

The Neanderthal in the mirror
A recent paper published in Molecular Biology and Evolution shows the presence of an x-linked haplotype in about 9% of all non-African populations. This would appear to be very strong evidence for significant interbreeding between Neanderthals and non-African populations. 

It is interesting how this plays out in discussions of human origins by non-specialists.  This blog post discusses what the author views as potentially racist interpretations of a related article.  Apparently some people are saying that because non-Africans had access to this additional (Neanderthal) gene pool it might have somehow made them more "evolutionarily advanced".  This is ridiculous. Remember, there weren't any Neanderthals (as far as we know) in Africa, hence it would have been pretty hard for African populations to mate with them, unless we are counting sexting. Clearly any claim that mating with Neanderthals makes you smarter/better/more evolved is just a post-hoc "what-if" claim that has no basis in the actual research.

The origin of malaria

Plasmodium infected red blood cell
If you have taken an introductory Anthropology course you have probably heard about malaria. It is a devastating killer disease in the tropics caused by an infection of the Plasmodium falciparum parasite which infects human blood cells.  We talk about it in intro anthro courses because of the relationship between malaria and another devastating disease, sickle cell anemia.  Sickle cell anemia is a genetic disorder caused by having two copies of the recessive gene which causes it. However, individuals which are merely carriers for the disease (having only one copy of the bad gene) don't get the anemia, and actually have increased resistance to malaria.  Its a classic case of a balanced polymorphism, and it explains why sickle cell anemia is prevalent in parts of the world where malaria is endemic.

In this article in PNAS, Prugnolle et al. discuss the possible origins of malaria, based a survey of the diversity of malarial parasites in several different monkey species in Central Africa.  They detected P. falciparum (the human killer) for the first time in monkeys.  This strain appears to be specific to non-human primates.  This opens up the possibility for a monkey source for human malaria, instead of the gorilla source which had been suggested by other workers.  This study is part of a fascinating recent revolution in primatology, involving the study of parasites from a genetic perspective.  I will take up that topic in a future post.