Evolution

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[T]wo subjects which moved my Father perhaps more deeply than any others were cruelty to animals & slavery – his detestation of both was intense, and his indignation was overwhelming in case of any levity or want of feeling on these matters.  – William Darwin

The trick to finishing books this year is getting up early, apparently.  I managed to get through the last four chapters of Darwin’s Sacred Cause this weekend while the baby slept. In the process, I’ve had to come to terms with  the disquieting beginnings of my own discipline and the bloody and violent antecedents of the town I’ve called home for the past dozen years.

Charles Darwin and Abraham Lincoln share a birthday, but they also share a tumultuous period in history. I’ve always been struck by the realization that Origin of Species was published just a few short years before the Civil War. After reading Darwin’s Sacred Cause, I get the idea that it was not coincidental.  Yes, Darwin sat on his big idea for 20 years, publishing travel journals, works on geology, and a four-volume monograph on barnacles. Why barnacles?  First, to document the amount of variation present in species, which natural selection requires to operate; and second, to establish himself as a knowledgeable naturalist in the eyes of the Royal Society, and provide the credentials needed to discuss his theory. In addition, describing the complete lineage of these marine arthropods provided an example of common descent. Barnacles were a proxy for a much more controversial topic – human variation.

Not science

Human variation is what I study as a biological (or physical) anthropologist. Physical anthropology has its roots, at least in part according to the authors, in phrenology. That’s the pseudo-science of determining temperament from the shape of the skull.  Not surprisingly, given that phrenology developed in Europe, Europeans were said to have the most refined skulls, and phrenological findings were used to justify slavery, something Darwin’s entire family was against.  Darwin would not have been impressed with the physical anthropologists of his day, especially in America, where differences in skull morphology were seen as “proof” of a polygenic origin of humans. According to the polygenists, each human “race” had its own pair of progenitors and were separately created, an idea used to justify all sorts of atrocities, since non-Europeans were seen as less than human. Darwin held the monogenist view, and saw all peoples as descended from a common ancestor, meaning they were all worthy of being treated with dignity and respect, and slavery was unjustified.  Actually, he took it farther than that, and saw a common ancestor for all living things.

It is absurd to talk of one animal being higher than another.–We consider those, where the cerebral structure/intellectual faculties most developed, as highest.–A bee doubtless would when the instincts were. – Charles Darwin

He spent a number of years studying pigeons, just to demonstrate that all the fancy breeds (“races”) descended from a common ancestor. Another proxy for human variation.

Darwin’s Pigeons – from Variation in Animals and Plants under Domestication (1868), with the common ancestor, the rock dove, in the center.

The tension between these two worldviews played out in my hometown, before the Civil War even started. In 1856, Sheriff Samuel Jones led a pro-slavery posse into Lawrence, Kansas, which had been established by abolitionist settlers two years before, sacked the town, burned the Free State Hotel, smashed the presses, and killed an antislavery supporter.

The ruins of the Free State Hotel

Darwin’s mentor and friend, geologist Charles Lyell, who encouraged him to publish his ideas on natural selection, was a Southern sympathizer. The Anthropological Society of London was founded in 1863, in the midst of the Civil War, with three Confederate agents on the council, whose sole purpose was to push a pro-slavery agenda.

Plaque on the site of the present-day Eldridge Hotel, 8th and Massachusetts, Lawrence, Kansas.

Plaque marking the site of the Free State Hotel, downtown Lawrence.

That’s what Darwin was up against.  Not just other naturalists, but Victorian society. No wonder he waited two decades to publish.

My discipline has come a long way since Darwin’s day.  The American Anthropological Association’s “Statement on Race and Intelligence” states in part:

WHEREAS all human beings are members of one species, Homo sapiens, and

WHEREAS, differentiating species into biologically defined “races” has proven meaningless and unscientific as a way of explaining variation (whether in intelligence or other traits),

THEREFORE, the American Anthropological Association urges the academy, our political leaders and our communities to affirm, without distraction by mistaken claims of racially determined intelligence, the common stake in assuring equal opportunity, in respecting diversity and in securing a harmonious quality of life for all people.

And the American Association of Physical Anthropologists has their own “Statement on Biological Aspects of Race,” which says:

Physical, cultural and social environments influence the behavioral differences among individuals in society. Although heredity influences the behavioral variability of individuals within a given population, it does not affect the ability of any such population to function in a given social setting. The genetic capacity for intellectual development is one of the biological traits of our species essential for its survival. This genetic capacity is known to differ among individuals. The peoples of the world today appear to possess equal biological potential for assimilating any human culture. Racist political doctrines find no foundation in scientific knowledge concerning modern or past human populations.

Image Credits:

Ryan Somma’s flickr stream

Wikimedia Commons

Dr. Steven M. Carr’s website

ResearchBlogging.orgSvante Pääbo’s group at the Max Plank Institute have a paper coming out in the February issue of Cell Biology. In it, they describe sequencing a complete early human mitochondrial genome from the Markina Gora specimen from the Kostenki 14 site in Russia. The remains date to around 30,000 years ago, not the oldest human sequence, but interesting nonetheless because the authors have identified new ways to determine if ancient DNA sequences are genuine vs. contamination.  This is especially important for more anatomically modern human fossils, who may have similar sequences to extant populations.

For Neandertal mtDNA, identifying contamination is relatively simple, because their mtDNA sequences fall outside the range of variation found in modern humans. Not so for more recent fossils.  So how can researchers identify true archaic sequences?

fragment length, deamination-induced sequence errors at ends of molecules, and purine-associated fragmentation represent features by which endogenous and contaminating populations of DNA molecules can be distinguished in at least some late Pleistocene specimens (1).

So, fragments sequenced from ancient samples are typically shorter than modern contaminants.  In many cases, the fragments are shorter than what can be amplified using PCR, meaning high-throughput direct sequencing methods are required to analyze these ancient samples.  In addition, the cytosine bases at the 5′ ends of ancient DNA fragments are susceptible to deamination (removal of an -NH3 group), causing those bases to be misread as thymine. The 3′ ends of ancient sequences have a commensurate increase in G-A errors. Finally, fragmentation of ancient sequences occurs more frequently at purine bases (guanine and adenine).

With these criteria in mind, the researchers determined that the Markina Gora sequence belongs to mitochondrial haplogroup U2, a haplogroup still present in Europe today.

Figure 3D from Krause et al. (2010) - with the EMH sequence highlighted in red.

The authors determine that it is unlikely that this sequence is the result of modern contamination, because the nucleotide difference between the Markina Gora specimen and the ancestral U sequence is much shorter than than seen between the root and modern sequences, which have accumulated many more mutations over time.  Their results also support the hypothesis of pre-agricultural genetic continuity in Europe, so that genetic lineages which were present on the continent prior to the Neolithic transition can still be found in modern European populations.

Krause J, Briggs AW, Kircher M, Maricic T, Zwyns N, Derevianko A, & Pääbo S (2009). A Complete mtDNA Genome of an Early Modern Human from Kostenki, Russia. Current biology : CB PMID: 20045327

Science Magazine has a YouTube channel!

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In celebration of the 150th anniversary of the publication of Darwin’s seminal work, On the Origin of Species, here are a few online resources.

The Complete Works of Charles Darwin Online – literally everything written by Darwin

Darwin’s Dangerous Idea – from the PBS Evolution series

Darwin’s Darkest Hour – If you missed the original airing last month, you can watch the entire program online.

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Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

– Charles Darwin, On the Origin of Species (1859)

What’s caught my attention this week:

Claude Levi-Strauss passes away at 100. One of the giants, instrumental in establishing the field of modern cultural anthropology.

NOVA: Becoming Human. The first episode in this three-part series aired on Tuesday, but you can watch it online. Nice update of recent fossil discoveries, and how they fit on the hominin evolutionary tree.

Illustration by John Gerrard Keulemans (1842-1912)

Illustration by John Gerrard Keulemans (1842-1912)

Whence the Falklands Wolf? – DNA analysis of museum specimens of an extinct canid species, one collected by Darwin on his journey aboard The Beagle, establishes their closest living relatives as the maned wolves of South America, suggesting the ancestors of the Falkland wolves rafted to the islands from the mainland.

Maned Wolf

Maned Wolf

Image Credits: Wikipedia – Falkland Islands Wolf, Wikipedia – Maned Wolf

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