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Archive for the ‘Human Evolution’ Category

Neanderthals in your past

May 6, 2010 3 comments

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Tomorrow’s Science will have a series of freely available papers on the Neanderthal genome. One claim is that that between 1% and 4% of the DNA of certain modern groups is attributable to hybridization between Homo sapiens and Neanderthals. Carl Zimmer and John Hawks have more. Jerry Coyne has a handy-dandy guide to the paper here.

The original paper is here and the abstract reads:

Neandertals, the closest evolutionary relatives of present-day humans, lived in large parts of Europe and western Asia before disappearing 30,000 years ago. We present a draft sequence of the Neandertal genome composed of more than 4 billion nucleotides from three individuals. Comparisons of the Neandertal genome to the genomes of five present-day humans from different parts of the world identify a number of genomic regions that may have been affected by positive selection in ancestral modern humans, including genes involved in metabolism and in cognitive and skeletal development. We show that Neandertals shared more genetic variants with present-day humans in Eurasia than with present-day humans in sub-Saharan Africa, suggesting that gene flow from Neandertals into the ancestors of non-Africans occurred before the divergence of Eurasian groups from each other.

(image source)

Orangs, Humans & ERVs

July 6, 2009 6 comments

Last week I briefly posted on the claim being made by John Grehan and Jeffrey Schwartz that morphological evidence indicates that the orang is our closest living relative and that molecular evidence accumulated over the past 40 years that the chimpanzee is closer is flawed and can be discarded. A vigorous discussion ensued and is still ongoing.

Last night I posted a question that remains unanswered by the proponents of the orang claim, so I’m going to repeat it here in a little more detail to see what we can ascertain. As a starter, let’s allow the claim that the molecular methods that support the Homo-Pan clade are flawed and should be discarded. How does a supporter of the Homo-Pongo clade explain the distribution of endogenous retroviruses within the great apes, a distribution that would appear to support the closer affinity of Homo and Pan.

retrovirus.gif

(Source: Lebedev, Y. B., Belonovitch, O. S., Zybrova, N. V, Khil, P. P., Kurdyukov, S. G., Vinogradova, T. V., Hunsmann, G., and Sverdlov, E. D. 2000 “Differences in HERV-K LTR insertions in orthologous loci of humans and great apes.” Gene 247: 265-277.)

Now it would appear (to me at least) that these results which are not dependent on the methods criticized by Grehan and Schwartz would unambiguously offer support for the Pan-Homo clade (and indeed the molecular phylogenies that they discard).

Thoughts?

Orangs in the family tree

June 29, 2009 61 comments

Many readers may be aware of the recent paper (in Journal of Biogeography no less) by Grehan and Schwartz claiming that there is sufficient morphological evidence to support the claim that orangutans are our closest living relatives, while simultaneously dismissing all of the genetic evidence for chimps being the closest living relative. John Hawks offers a succinct reply, one which is supported by my (admittedly rushed) reading of the paper.

Ref: John R. Grehan & Jeffrey H. Schwartz. Evolution of the second orangutan: phylogeny and biogeography of hominid origins. Journal of Biogeography, 2009 DOI: 10.1111/j.1365-2699.2009.02141.x

Update (6/30): The paper is available online here.

Darwinius masillae gets out of control

May 20, 2009 1 comment

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Can’t help but feel that this is getting a little silly. Darwinius masillae is a nice beautifully preserved specimen, it’s an interesting specimen, but it’s not THE missing link. Bora has complete links to the media circus while Ed Yong puts it all in perspective.

For more on this, see:

  • The original paper: Franzen JL, Gingerich PD, Habersetzer J, Hurum JH, von Koenigswald W, Smith BH (2009) “Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology.” PLoS ONE 4(5): e5723. doi:10.1371/journal.pone.0005723
  • PZ Myers over at the Panda’s Thumb.
  • John Wilkins on missing links and ancestors.
  • Carl Zimmer asks the question, does Darwinius even exist? It appears that PLoS may not count as a valid venue to publish taxonomic work.

Somewhat predictably, Matt Nisbet approves of this “innovative strategy“. Given that, this quote by Phil Gingerich in The Australian is of interest:

[O]ne of Dr Hurum’s co-authors, University of Michigan paleontologist Philip Gingerich, said the team would have preferred to publish in a more rigorous journal such as Science or Nature.

Dr Gingerich told The Wall Street Journal: “There was a TV company involved and time pressure. We’ve been pushed to finish the study. It’s not how I like to do science”.

Media-driven science with a book, movie & website. Nisbet’s “going broad” strategy has seen the light of day. Just what we need.

Remembering Charlie Lockwood

April 27, 2009 Comments off

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My colleague and friend Kaye Reed has a nice remembrance of Charlie Lockwood in the current issue of Evolutionary Anthropology. I had reason to mention Charlie during my “Last Lecture” and will admit to getting a little choked-up. The article is unfortunately behind a paywall, but any good university library should have access.

[Review] Explaining Human Origins

July 27, 2008 1 comment

(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 cultural accretions, we are having so little success in generating a conclusive narrative about hominization.

Read more…

Sad news for the anthropology community

July 14, 2008 9 comments

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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 geometric morphometrics to study temporal bone variation in hominins. Three papers resulted:

  • Lockwood,C.A., Lynch,J.M., Kimbel,W.H. (2002). Quantifying temporal bone morphology of great apes and humans: An approach using geometric morphometrics. Journal of Anatomy 201(6), 447-464.
  • Lockwood,C.A., Kimbel,W.H., Lynch,J.M. (2004). Morphometrics and hominoid phylogeny: Support for a chimpanzee-human clade and differentiation among great ape subspecies. Proceedings of the National Academy of Sciences USA 101(13), 4356-4360.
  • Lockwood,C.A., Kimbel,W.H., Lynch,J.M. (2005). Variation in early hominin temporal bone morphology and its implications for species diversity. Transactions of the Royal Society of South Africa 60(2), 73-77.

There was other research we intended to do but, somehow, with Charlie’s move to London in 2004 and all that involved, we never got round to it. He was soon to be returning to South Africa to take a position at Wits. I’m proud to have known Charlie as a colleague and a friend. He will be missed.

Update: Charlie gets a mention from Adam Yates, Anthropology.net, Greg Laden & John Hawks.

New evidence for human evolution discovered

March 29, 2008 6 comments

greatape

Seed has been running an interview with the British author Will Self whom I first encountered by reading his wonderful Great Apes, the cover of which – a mash-up of a human and ape – is above. Every time I see this picture, I can only think of one person …

Read more…

A new date for chimp/human divergence

February 24, 2007 3 comments

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According to this paper, a hidden Markov model of the divergence between humans and chimps finds “a very recent speciation time of human-chimp (4.1 ± 0.4 million years)”. This would put the last common ancestor with Pan after a previously
reported
date of between 4.98 and 7.02 million years. (TimeTree reports the weighted average for the time of nuclear divergence to be 5.56 million years). The age of 4.1 million years would apparently put the split during the time of such taxa as Australopithecus anamensis, A. afarensis and Kenyanthropus platyops. It will be interesting to see how this affects our current understanding of hominid evolution.

Ref: Hobolth A, Christensen OF, Mailund T, Schierup MH (2007) Genomic Relationships and Speciation Times of Human, Chimpanzee, and Gorilla Inferred from a Coalescent Hidden Markov Model. PLoS Genet 3(2): e7 doi:10.1371/journal.pgen.0030007

Killing our faith

February 6, 2007 5 comments

turkana

This is Turkana boy (Homo ergaster), soon to go on display in Kenya’s national museum. Bishop Boniface Adoyo, of Nairobi Pentecostal Church (NPC) and Christ is the Answer Ministries, claims:

“I did not evolve from Turkana Boy or anything like it. These sorts of silly views are killing our faith.”

Someone should explain to Adoyo that the truth sometimes hurts. Speaking of “silly views,” apparently, Adoyo believes the world was created 12,000 years ago, humans were created 6,000 years ago, and each biblical day was equivalent to 1,000 Earth years. I guess nothing in Adoyo’s BA in design prepared him to think about the geological record or palaeontology.

Human-Neanderthal Hybridization (here we go again … again)

January 17, 2007 2 comments

A day or so back, I posted on an AP article which declared that “skull found in a cave in Romania includes features of both modern humans and Neanderthals, possibly suggesting that the two may have interbred thousands of years ago.” The original research article is now online. Let’s look at the abstract, shall we?

Between 2003 and 2005, the Pestera cu Oase, Romania yielded a largely complete early modern human cranium, Oase 2, scattered on the surface of a Late Pleistocene hydraulically displaced bone bed containing principally the remains of Ursus spelaeus. Multiple lines of evidence indicate an age of {approx}40.5 thousand calendar years before the present ({approx}35 ka 14C B.P.). Morphological comparison of the adolescent Oase 2 cranium to relevant Late Pleistocene human samples documents a suite of derived
modern human and/or non-Neandertal features, including absence of a supraorbital torus, subrectangular orbits, prominent canine fossae, narrow nasal aperture, level nasal floor, angled and anteriorly oriented zygomatic bones, a high neurocranium with prominent parietal bosses and marked sagittal parietal curvature, superiorly positioned temporal zygomatic root, vertical auditory porous, laterally bulbous mastoid processes, superiorly positioned posterior semicircular canal, absence of a nuchal torus and a suprainiac
fossa, and a small occipital bun. However, these features are associated with an exceptionally flat frontal arc, a moderately large juxtamastoid eminence, extremely large molars that become progressively larger distally, complex occlusal morphology of the upper third molar, and relatively anteriorly positioned zygomatic arches. Moreover, the featureless occipital region and small mastoid process are at variance with the large facial skeleton and dentition. This unusual mosaic in Oase 2, some of which is paralleled
in the Oase 1 mandible, indicates both complex population dynamics as modern humans dispersed into Europe and significant ongoing human evolution once modern humans were established within Europe.

Umm. No mention of hybridization. So what does the main text say?

The potential phylogenetic scenarios could involve evolutionary reversals relative to the presumably ancestral MPMH [Middle Paleolithic Modern Humans], the appearance of a uniquely derived set of traits in the lineage leading to the Oase remains, and/or reflect incomplete paleontological sampling of Middle Paleolithic human diversity. In this case, Oase 2 could indicate only descent from earlier MPMH. Alternatively, it could reflect admixture with Neandertal populations as oxygen isotope stage
3 modern humans spread through western Eurasia, as suggested elsewhere (1, 10, 28-32). This mixture would have resulted in both archaic traits retained from the Neandertals and unique combinations of traits resulting from the blending of previously divergent gene pools. The ultimate resolution of these issues must await considerations oflarger samples of MPMH, European early modern humans, and chronologically intervening specimens.

Draw your own conclusions.

Human-Neanderthal hybridization (here we go again …)

January 15, 2007 3 comments

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AP is reporting that a “skull found in a cave in Romania includes features of both modern humans and Neanderthals, possibly suggesting that the two may have interbred thousands of years ago.” A paper to appear in Tuesday’s PNAS (and not online yet) will argue that the ~40,000 year old skull raises “important questions about the evolutionary history of modern humans,”

Out of Africa

January 11, 2007 2 comments

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A fossil skull discovered in 1952 offers support for the hypothesis that Upper Paleolithic Eurasians descended from a population that emigrated from sub-Saharan Africa in the Late Pleistocene. In tomorrow’s Science, Fred Grine and co-workers describe a South African skull dated to 36.2 ± 3.3 thousand years, and note that while the skull is morphologically modern overall, its strongest morphometric affinities are with Upper Paleolithic Eurasians rather than
recent, geographically proximate people.

The paper is available here (subscription required).

Little Lucy

September 21, 2006 Comments off

A number of my SciBlings has already covered the discover of the three-year old Australopithecus afarensis skeleton that has been dubbed “Little Lucy” (see, for example, PZ’s post). I’m just going to point out the the specimen was discovered and described by individuals associated with Arizona State University’s Institute of Human Origins, in particular Bill Kimbel with whom I have in the past worked with on temporal bone variation. Great stuff!

Australopith ancestry clarified

April 12, 2006 6 comments

From UC Berkeley:

New fossils discovered in the Afar desert of eastern Ethiopia are a missing link between our ape-man ancestors some 3.5 million years ago and more primitive hominids a million years older, according to an international team led by the University of California, Berkeley, and Los Alamos National Laboratory in New Mexico.
The fossils are from the most primitive species of Australopithecus, known as A. anamensis, and date from about 4.1 million years ago, said Tim White, a UC Berkeley professor of integrative biology and one of the team’s leaders. The hominid Australopithecus has often been called an ape-man because, though short-statured, small-brained and big-toothed, it walked on two legs unlike the great apes.
More primitive hominids in the genus Ardipithecus date from between 4.4 million and 7 million years ago and were much more ape-like, though they, too, walked on two legs.
“This new discovery closes the gap between the fully blown Australopithecines and earlier forms we call Ardipithecus,” White said. “We now know where Australopithecus came from before 4 million years ago.”
The fossil finds and an analysis of the hominid’s habitat and evolutionary position are reported by White and co-authors from Ethiopia, Japan, France and the United States in the April 13 issue of Nature.

You can read more here.
Edit: The paper is now online here.
White et al. (2006) “Asa Issie, Aramis and the origin of Australopithecus” Nature 440, 883-889 (13 April 2006) | doi:10.1038/nature04629

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