Monday, November 9, 2009

New Paper on Human Uniqueness

A new paper in Evolutionary Anthropology reviews the causes of the global expansion of homo sapiens and argues that it was our propensities for cooperation and social learning that made this ecological dominance possible. The paper initially takes a distinctly macroecological perspective on the evolution of human culture, by commenting on some general facts reflecting the evolutionary success of humans.

The emergence of human uniqueness: Characters underlying behavioral modernity
Kim Hill, Michael Barton, A. Magdalena Hurtado
email: Kim Hill ( Michael Barton ( A. Magdalena Hurtado (

Although scientists are aware that humans share the same biological heritage as do all other organisms on the planet, the reliance of Homo sapiens on culture and cooperation has resulted in what can best be described as a spectacular evolutionary anomaly.1:11 The extra-somatic adaptations, technological dominance, and success of our species in colonizing every terrestrial habitat have no parallel.2 Moreover, Homo sapiens accounts for about eight times as much biomass as do all other terrestrial wild vertebrates combined,3 an amount equivalent to the biomass of all 14,000+ species of ants,4 the most successful terrestrial invertebrates. Human societies are complex, with more specialized economic niches in the United States than the total number of mammalian species on the planet.5 While some might suggest that only post-industrial humans achieved stunning biological success, data suggest that humans living as hunter-gatherers would have attained a world population of more than 70 million individuals6 and a total biomass greater than that of any other large vertebrate on the planet if agriculture had not been repeatedly invented as they spread.

"we outline a series of preadaptations that may help explain why later Homo evolved unique traits that chimpanzee, elephant, and porpoise lineages did not. Other apes have large brains, regularly engage in social learning, and exhibit theory of mind. Moreover, those ape species also passed through the Pleistocene without evolving the combination of characters that make humans biological outliers. We must, therefore consider important preadaptations in the genus Homo that led to human uniqueness.”

This is an excellent review paper that I'm sure will get a lot of attention. Its interesting to see human behavioral ecologists paying progressively more attention to cultural evolution and group level dynamics as major driving forces in the expansion of homo sapiens. I might add that this topic general, that is asking the big 'why questions' about what factors made humans such an expansive force as Pleistocene hunter-gatherers, receives strikingly little attention from evolutionary ecologists.

Thursday, January 29, 2009

First Americans Paper in PNAS

PNAS published a review paper on the peopling of the Americas authored by Tom Dillehay.
I have to say it strikes me as kind of an odd paper to appear in a journal like PNAS. Its title is 'Probing Deeper into First American Studies' and yet it really doesn't report anything new and as a review paper goes the synthesis of existing data is just sort of... so so. Also interesting is that even though it explicitly addresses different ideas about how the New World was colonized, it does not cite a paper written on this very topic that was published in this very journal within the last year. Is that odd? I think so. Especially since its a novel and interdisciplinary approach to understanding migrations and that is exactly what Dillehay says we need more of...
Here's a quote from the paper:

"Places of origin, dates of entry, routes of dispersion, and types of early cultural lifestyles lie at the heart of the debate over the initial peopling of the Americas. Fresh thinking about these and other issues has occurred because of the recent demise of the Clovis-first paradigm to explain the initial peopling of the Americas (2, 6, 7, 8) and because of new and more flexible interdisciplinary research directions."

I have to admit I'm also a bit tired of the Monte Verde crowd claiming that the 'Clovis-first paradigm' has been defeated because of sites like, well... Monte Verde, which is much more problematic than we're aloud to acknowledge. If you do question it, prepare to be berated by Dillehay and his friends. (Also, 'paradigm' ? really? clearly Clovis-first is nothing like an actual paradigm as defined by Thomas Kuhn. Just a pet peeve...)

Just the same, this will continue to be a hot topic in archaeology and hopefully the issues raised in this short reivew will be resolved with new data and research in the future.

Sunday, January 25, 2009

Water bears: just because everyone should know about these

This doesn't come from an obscure source or anything like. Just NPR's Science Friday, but here's a very cool video they posted on their website. Enjoy it.

Monday, June 9, 2008

An idea worth spreading

Here's a video of a lecture by Ron Eglash about fractals in Africa. its quite interesting in terms of the small bit of history of fractals you get as well as in terms of those he discovers in African settlements and art. I don't know if its true that fractals are not just as present outside of Africa but this is cool. I thank Chris Millington for sending this.
The video is part of the TED series - I posted one before. Its just shy of 17 minutes long.

Monday, April 7, 2008


The semester got away from me a bit and I've been terrible about getting anything posted for a while now. I was at the Society for American Archaeology meetings in Vancouver last week, which were great fun and I should blog about them. That is why I missed a week in the series on Foraging. I hope to get rolling again soon. The other big event is of course the SWARM meetings, which are later this week - lots to get together for those...

Thursday, March 20, 2008

Humans and extinctions: the flightess sea duck

A paper just published in PNAS argues that since the flightless sea duck didn't got extinct until well into the Holocene humans probably didn't hunt megafauna to extinction. No, seriously.

Here's the title, and abstract:
The protracted Holocene extinction of California's flightless sea duck (Chendytes lawi) and its implications for the Pleistocene overkill hypothesis

T. L. Jones, J. F. Porcasi, J. M. Erlandson, H. Dallas, Jr., T. A. Wake, an R. Schwaderer

Bones of the flightless sea duck (Chendytes lawi) from 14 archaeological sites along the California coast indicate that humans hunted the species for at least 8,000 years before it was driven to extinction. Direct 14C dates on Chendytes bones show that the duck was exploited on the southern California islands as early as {approx}11,150–10,280 calendar years B.P., and on the mainland by at least 8,500 calendar years B.P. The youngest direct date of 2,720–2,350 calendar years B.P., combined with the absence of Chendytes bones from hundreds of late Holocene sites, suggests that the species was extinct by {approx}2,400 years ago. Although the extinction of Chendytes clearly resulted from human overhunting, its demise raises questions about the Pleistocene overkill model, which suggests that megafauna were driven to extinction in a blitzkrieg fashion by Native Americans {approx}13,000 years ago. That the extermination of Chendytes was so protracted and archaeologically visible suggests that, if the terminal Pleistocene megafauna extinctions were primarily the result of human exploitation, there should also be a long and readily detectable archaeological record of their demise. The brief window now attributed to the Clovis culture ({approx}13,300–12,900 B.P.) seems inconsistent with an overhunting event.


There is also an accompanying commentary by Donald Grayson.

The authors have thoroughly documented an interesting relationship between human predation and this species of flightless duck. There seems little doubt that the duck was periodically or frequently preyed upon for millennia before it went extinct. They argue that the early inhabitants of the California coast were more technologically sophisticated than is generally acknowledged - they had some boats/canoes from which to hunt. What I don't understand is the lack of attention to ecology when they try to make the leap of connecting the relationship they document to Pleistocene extinctions in general. So maybe people had boats 12,000 years ago but I think its worth considering that there are some pretty fundamental differences between mammoths and ducks... (!!) and the particular island environments where most island extinctions took place are also different from the California coast. The colonists didn't bring rats, the environment was not as circumscribed as many islands and may have provided more natural refugia from human predation, the people may have had their main populations on the coast rather than on islands (in the california case), and they may have been at lower population densities.

Grayson's commentary is surprisingly even-handed. He seems more conservative with regard to the suggestion that this particular history of this particular species of flightless bird has general implications for our thinking of the loss of megafauna. But rather suggests that understanding the processes of extinction on a species by species basis tells us that there some important nuances that are often overlooked and that in many cases direct predation may not be the mechanism of extinction. Humans alter environments in lots of ways and it may be these indirect effects that are often detrimental. Rats and dogs and pigs all likely accelerated the rate of extinction in the case of Polynesian colonists.

Grayson and Jones et al (and lots of other archaeologists) frequently point out that the evidence for association between unambiguous signs of human activity and the remains of the extinct megafauna are rare in North America. And that is part of the point Jones et al are making. That this species has loads of direct associations with people and hence the extinction process is very visible. So why isn't it more visible for sloths and other really large critters that went extinct and should be very visible? If people were butchering these animals in a more expedient manner and not transporting bones to caves and rock shelters very often, then that could explain the lack of well preserved evidence. (I suppose). They also point out that the process of human mediated extinction seems to take a really long time in some cases, even islands, and yet for 35 genera across the entire continent of North America it was very rapid.

Good points in the article and in the commentary... would have liked to see more discussion of the ecological variables that alter the probability of extinction.


Monday, March 17, 2008

SWARM schedule posted

The blog post for the upcoming SWARM meetings has been updated with more detailed scheduling information. The Human Macroecology symposium will be on Thursday April 10, 2008. Read more about it here.

Tuesday, March 11, 2008

More very small humans found

An exciting discovery was recently made and just reported on in PLoS One. Several (25ish) individuals of very small and potentially insularly dwarfed humans were found on the island of Palau, which is within spitting distance (relatively speaking of course) of the well known and hotly debated finds from Flores.

title and authors are:

Small-Bodied Humans from Palau, Micronesia

Lee R. Berger, Steven E. Churchill, Bonita De Klerk, Rhonda L. Quinn

Its an open access article so you can get it here.
A blog written about the find has been posted on, which you can read here.
These finds are much more recent, dating to the last 3000 years than the ones from Flores, which are 18,000 years old or so. They were found in cave sites which appear to be burial locations as very few artifacts and no other fauna are associated.
The authors interpret the findings as dwarfed homo sapiens rather than some genetic abnormality as has been argued for the Flores finds (and contests as well of course).
There are some similarities between these Paluan finds and the ones from Flores.

Here is the final paragraph of the paper to offer their conclusions:

"Based on the evidence from Palau, we hypothesize that reduction in the size of the face and chin, large dental size and other features noted here may in some cases be correlates of extreme body size reduction in H. sapiens. These features when seen in Flores may be best explained as correlates of small body size in an island adaptation, regardless of taxonomic affinity. Under any circumstances the Palauan sample supports at least the possibility that the Flores hominins are simply an island adapted population of H. sapiens, perhaps with some individuals expressing congenital abnormalities."

It will be interesting to see how the different sides of the Flores arguments react to these findings.
Great stuff. exciting to think about. human biogeography.


Saturday, March 8, 2008

A little primate biogeography

A fairly recent PNAS paper makes some interesting claims about the first primates to arrive in the New World. These little mouse sized guys, called Teilhardina magnoliana may have arrived by crossing the landbridge between Siberia and the New World way before people did (like 60 million years ago or so). They tip the scales at around 28 grams.

A good popular news piece based on the article can be found here.

Here's the stuff on the PNAS paper:

The oldest North American primate and mammalian biogeography during the Paleocene–Eocene Thermal Maximum

K. Christopher Beard{dagger}

Section of Vertebrate Paleontology, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, PA 15213

Edited by Alan Walker, Pennsylvania State University, University Park, PA, and approved January 10, 2008 (received for review October 25, 2007)


Undoubted primates first appear almost synchronously in the fossil records of Asia, Europe, and North America. This temporal pattern has complicated efforts to reconstruct the early dispersal history of primates in relation to global climate change and eustatic fluctuations in sea level. Here, I describe fossils from the Tuscahoma Formation on the Gulf Coastal Plain of Mississippi documenting an anatomically primitive species of Teilhardina that is older than other North American and European primates. Consistent with its antiquity, a phylogenetic analysis of dental characters recognizes Teilhardina magnoliana, sp. nov., as the most basal member of this genus currently known from either North America or Europe. Its stratigraphic provenance demonstrates that primates originally colonized North America near the base of the Paleocene–Eocene Thermal Maximum (PETM), but before an important fall in eustatic sea level. Correlation based on carbon isotope stratigraphy and sequence stratigraphy indicates that the earliest North American primates inhabited coastal regions of the continent for thousands of years before they were able to colonize the Rocky Mountain Interior. The transient provincialism displayed by early North American primates corresponds to similar biogeographic patterns noted among fossil plants. Decreased precipitation in the Rocky Mountain Interior during the early part of the PETM may have been an important factor in maintaining biotic provincialism within North America at this time. These results underscore the need to obtain multiple, geographically dispersed records bearing on significant macroevolutionary events such as the PETM.

Cosmic impacts and the end-Pleistocene extinction: idea seems not to hold up

A while back I posted a blog on a paper published in PNAS arguing that a comet impact was responsible for the extinction of the megafauna in North America. They also argue that the impact was responsible for the disappearance of the Clovis culture - the earliest recognized archaeological culture in the New World known for large well made and very distinctive fluted spear points.
I was skeptical of their ability to link the proposed impact to the strongly size biased nature of the extinctions and wondered about how it extended to the similar patterns in extinction that we see on other continents. There was a lot missing in terms of how to link the impact to mammals - but aside from that it seemed like they may have demonstrated that lots of stratigraphic layers around the United States contain minerals of extra-terrestrial origin. or maybe not...

A news focus just published in Science (authored by Science writer Richard Kerr) reviews the evidence and points out that many of the claims by the authors of the comet study are not holding up. This is probably not surprising on the whole but it is amazing how many of the claims seem to be really thoroughly refuted and experts in the study of cosmic impacts suggest that the hole's in the study were evident long before it was published - that can happen when papers go to non-specialized audiences. Also note that the paper was published in PNAS...

Magnetic spherules believed to be diagnostic of the impact were a key line of evidence for the study by Firestone et al. (the authors of the PNAS paper) but it turns out that such spherules may be regularly introduced to our atmosphere from space and are not useful markers for a specific impact.

Excerpt from the article:
"One problem is that no one has "any of the classic evidence of an impact," says impact specialist David Kring of the Lunar and Planetary Institute in Houston, Texas. Spurred by the 1980s debate over what killed off the dinosaurs, "the community learned a lot about what the threshold of evidence is" for confirming an impact, he explains. But taking all the evidence offered by the group proposing the mammoth-killer impact, "you end up with [markers] that are not diagnostic of impact," says impact specialist Bevan French of the National Museum of Natural History in Washington, D.C. Proponents, meanwhile, are defending some of their published claims and giving ground on others but promising ultimate vindication.

Figure 2 ET? An impactor (top) may have produced magnetic spherules (lower right), but similar spherules (lower left) continually fall from space.


Diamonds not forever
Everyone agrees on one point at least. "Obviously, something really interesting happened 13,000 years ago," as Kring puts it. It was 12,900 years ago, to be precise, that a world staggering out of the last Ice Age suddenly plunged back into a millennium of near-glacial climate before emerging into the current warmth. It was also about then--emphasis on the uncertainties summed up by "about"--that the mammoths and other great beasts disappeared from North America. And the Paleo-Indian Clovis culture vanished from the archaeological record around then, too."
Science 7 March 2008:
Vol. 319. no. 5868, pp. 1331 - 1332
DOI: 10.1126/science.319.5868.1331

Experts question the existence of the nanodiamonds that are thought to be traced to the impact and other lines of evidence, such as the iridium spike in the stratigraphic layers in question, have been fairly extensively criticized and questioned as well.

These criticisms really don't sound like the nay-saying that goes with old stodgy types not like their conventional wisdoms being questioned. They seem pretty solid. Perhaps the debate will continue to play out in the literature.

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