After Darwin at AMNH: Ian Tattersall

Thursday, February 04 5:26 pm

Curator Ian Tattersall on Darwin’s Thoughts About the Fossil Evidence for Human Evolution

Scientists at the American Museum of Natural History continue to celebrate the 200th anniversary of Charles Darwin’s birth and the 1859 publication of On the Origin of Species with a collection of vignettes describing expeditions and ideas with links to Darwin’s seminal work.

Below is an excerpt of a longer piece that Ian Tattersall wrote for Evolution: Education and Outreach in 2009.

Charles Darwin was curiously unforthcoming on the subject of human evolution as viewed through the fossil record, to the point of being virtually silent. He was, of course, most famously reticent on the matter in On the Origin of Species, … [and] this is true even of his 1871 book The Descent of Man, and Selection in Relation to Sex in which Darwin finally forced himself to confront the implications of his theory for the origin of humankind [but in which he barely managed even a passing reference to the Neanderthal fossil that by then was the subject of extensive scientific speculation.]

There were…many reasons why Darwin should have been disposed in The Descent of Man to shrink from any substantive discussion of whether extinct human relatives might actually be represented in fossil form. The fossil and antiquarian records were awash with fakes; any discussion of human ancestry was rife with social and political pitfalls; and anyway, by his own close colleague’s testimony, the record contained nothing that could have any relevance to ancient and now-extinct human precursors. Add to that Darwin’s innate suspicion of the distorting effects of incompleteness in the fossil record, and he may have felt that a large degree of discretion on the matter was mandatory.

The Feldhofer skullcap--the Neanderthal type specimen-- was discovered in a limestone cave in 1857 and is one of a handful of fossils that Darwin could have been aware of while writing The Origin of Species. The image includes an associated zygomaticomaxillary fragment that was discovered in the miners’ dump almost a century and a half later, in 1997. Credit: AMNH

None of this means, of course, that The Descent of Man has not exerted an immense influence on the sciences of human origins over the last century and a half. Just as it is easy for English speakers to forget how much they owe to William Shakespeare for the language they use daily, we tend to lose sight of the fact that much received wisdom in paleoanthropology has come down to us direct from Darwin. Darwin it was who proposed a mechanism for the structural continuity of human beings with the rest of the living world and who gave a detailed argument for human descent from an “ape-like progenitor.” It was Darwin who documented beyond doubt, in The Descent of Man, that all living humans belong to a unitary species with a single origin—which we now know, on the basis of evidence of which Darwin could never have dreamed, to have been around 200,000 years ago. He also had the inspired hunch that our species originated in the continent of Africa—and again, this guess has been amply substantiated by later science. Darwin’s perceptions on the behaviors of other primates and how they relate to the way humans behave were remarkably astute, particularly given the highly anecdotal nature of what was then known. Read more »

After Darwin at AMNH: David Hurst Thomas

Thursday, January 28 4:29 pm

Curator David Hurst Thomas Tests Darwin in Archaeological Sites

Scientists at the American Museum of Natural History continue to celebrate the 200th anniversary of Charles Darwin’s birth and the 1859 publication of On the Origin of Species with a collection of vignettes describing expeditions and ideas with links to Darwin’s seminal work.

Part of the St. Catherines archaeology team shucking oysters to determine the amount of energy (in calories) that people can retrieve in relation to the amount of energy spent collecting and processing. Credit: Lorann S.A. Pendleton.

Deer, clams, oysters, alligators: if you walked the length of St. Catherines Island off of Georgia, what would you pop into your mouth? David Hurst Thomas, curator in the Division of Anthropology at the Museum, uses optimal foraging theory to interpret the remains of thousands of meals left behind in archaeological sites across the island.

Optimal foraging theory puts an evolutionary spin on what people chose to eat. The assumption that individuals decide what to consume in a way that maximizes the total energy return and minimizes the energy they must spend to search for, collect, and prepare food items in their environment. This approach is known as the “diet breadth model,” a series of testable hypotheses about what an efficient forager will pick (and not pick) from the array of available food.

“Darwinian evolutionary ecology allows us to frame some concrete expectations about what a forager should choose to gather,” says Thomas. “Suppose someone dropped a pot of coins. Some would be selective, picking up only silver dollars, and others would rush to pick up everything. The diet breadth model allows us to distinguish between these strategies in archaeological sites.”

Thomas and his team have spent more than 30 years excavating different archaeological sites throughout the island’s 14,000-plus acres. Recently, the team conducted a series of foraging experiments that, as Thomas puts it, “hook theory to dirt archaeology” by mapping the most efficient strategies for harvesting the available foodstuffs. They harvested oysters, dug up clams, butchered diamondback terrapins, and drank periwinkle soup. For each food type, the archaeologists recorded the length of time and amount of energy expended for collecting and processing. These data were then compared to the amount of available energy gained from food to answer a key question: if I invest one hour in foraging, what is the energetic return on that investment? The result, expressed as kilocalories per hour, allows researchers to compare different food types. Read more »

After Darwin at AMNH: Rob DeSalle

Monday, December 14 10:19 am

Curator Rob DeSalle Explains the Limitations of Genetic Ancestry Tests

This year, scientists at the American Museum of Natural History are celebrating the 200th anniversary of Charles Darwin’s birth and the 1859 publication of On the Origin of Species with a collection of vignettes describing expeditions and ideas with links to Darwin’s seminal work.

An annotated academic poster from a conference held at AMNH in 1932 shows the inheritance of two genetic sequences commonly used in ancestry testing. On top of Charles Darwin’s pedigree, DeSalle plotted mitochondrial DNA in red and Y-chromosome in blue. Darwin is outlined by a blue square. - AMNH

When Henry Louis Gates Jr., Harvard University professor and host of the PBS series African American Lives, learned that his Y-chromosome—a gene popularly used to trace male ancestry—“goes back to Europe,” he joked that he was having an identity crisis. And in his best-selling book The Seven Daughters of Eve geneticist Brian Sykes suggests that 95% of all Europeans are descended from just seven Stone Age women. He used mitochondrial DNA, inherited directly from mothers and employed by companies for ancestry testing of the maternal ancestry, for this work.

These are dramatic moments, but they are based in part on misleading assumptions, according to geneticists like Rob DeSalle, Curator in the Sackler Institute for Comparative Genomics at the Museum. “Ancestry testing is pushed as simple and straight-forward,” he says. “But it is not. Often the verbal history passed down in families is more accurate than ancestry DNA testing done now.”

DeSalle, along with Museum colleague Ian Tattersall, turned to the family history of the most famous of evolutionary thinkers to illustrate their point. By simply mapping basic inheritance onto Charles Darwin’s pedigree, it is easy to see how quickly a specific Y-chromosome or sequence of mitochondrial DNA (mtDNA) can be lost in a lineage. Darwin’s Y-chromosome, for example, is probably found in only two of his living descendents. Only three of his four sons reproduced and one of these sons only had daughters. Ultimately, the number of male descendents of Darwin’s two sons who had male offspring dwindled to a very small number. There are many direct male descendents of Charles Darwin living today, but most of them do not have his Y chromosome. Read more »

Rare Darwin Manuscript Goes Digital

Monday, December 07 10:22 am

When Charles Darwin labored over word choice while writing On the Origin of Species by Means of Natural Selection, he could not have known that one day absolutely anyone could peer over his shoulder to see him pen the words, “difficulty of highly perfect organs.”

But now, Darwin’s scientific drafts, notes, and texts are going online. Anyone can now read 34 of the 36 known and located draft leaves of On the Origin, gathered together for the first time since Darwin wrote this seminal book. These rare documents are a tiny portion of the 10,000 high-quality images that will become part of the Darwin Manuscripts Project, a collaboration between the American Museum of Natural History, Cambridge University Library, and the Biodiversity Heritage Library (Natural History Museum in London).

“These rare manuscript leaves from On the Origin are the crown jewels of our project and show Darwin in the process of writing,” says David Kohn, Director and General Editor of the Project. “I’ve sat in the Cambridge University Library since 1974, touching these documents, but this is the first time that anyone can do this—online, in this quantity, and with this quality.”

After Darwin at AMNH: John Flynn

Friday, November 20 3:51 pm

Fossil Hunting Among Volcanoes With Paleontologist John Flynn

This year, scientists at the American Museum of Natural History are celebrating the 200th anniversary of Charles Darwin’s birth and the 1859 publication of On the Origin of Species with a collection of vignettes describing expeditions and ideas with links to Darwin’s seminal work.

It was during a siesta in the woods that Charles Darwin, exploring the Chilean coast more than three years into his voyage on the H.M.S. Beagle, was shaken by one of the strongest earthquakes known to the local inhabitants. On that February day in 1835, Darwin not only witnessed “the most awful spectacle I ever beheld… [with] not one house left habitable,” as he wrote to his sister Caroline, but he also had an epiphany:

The most remarkable effect of this earthquake was the permanent elevation of the land… [which revealed] mussel-shells still adhering to the rocks, ten feet above high-water mark.… At Valparaiso… similar shells are found at the height of 1,300 feet: it is hardly possible to doubt that this great elevation has been effected by successive small uprisings.

Chilecebus, a reconstruction of which is shown above, is one of the fossils that John Flynn and colleagues have uncovered in the Chilean Andes (Illustration by Velizar Simeonovski, courtesy of John J. Flynn)

While sailing across the Atlantic and past Tierra del Fuego, Darwin had been reading Charles Lyell’s Principles of Geology, in which Lyell laid out the case that massive geological change is based on the slow accumulation of minute changes over time. It was through this lens that Darwin observed the volatile, shifting landscapes that partly informed his theory of evolution.

We now know that the active geology of Chile—the earthquakes, volcanoes, and formation of the Andes Mountains themselves—is caused by the squeezing of the Pacific Ocean plate under South America and back into the Earth’s interior. Paleontologist John Flynn and colleagues André Wyss, Reynaldo Charrier, and Darin Croft have traversed this geology over the last 20 years to learn more about both the history of the Andes and the unusual extinct fauna that lived on this former island continent. Mountain uplift drives fossil beds to the surface, weathering exposes fossil teeth and bone, and volcanic debris dates their time frames.

“We were first drawn to Chile because amateur naturalists found whale bones at 6,000 feet in the 1980s,” says Flynn. “Since then, we’ve uncovered a remarkable mammalian menagerie that explains some of the diversity seen today and also helps us understand more of the uplift history of this 5,000-mile-long mountain chain that forms a spine along then entire western edge of South America.” Read more »