Early elephants were aquatic feeders

Elephants, even now, love water. And they come by it honestly. In the Eocene period, 37 million years ago, the ancestors of elephants spent time in the water probing with their proto-trunks for aquatic plants to eat. It’s possible that the elephant’s trunk developed initially for reaching deep into the water for forage.

Moeritherium (Luci Betti-Nash/Stony Brook University)

Two early proboscideans, Moeritherium andBarytherium, have left fragmentary remains. To tell what they ate, researchers looked at the distribution of isotopes in their teeth. The isotopes reflect a watery environment.

While carbon isotopes can give clues as to an animal’s diet, oxygen isotopes found in teeth come from local water sources – and variations in the ratios of these isotopes can indicate the type of environment the animal lived in. They compared the ratios of these isotopes to definitely terrestrial animals from the same period and these results – when combined with results from studies of embryology, molecular data, and sedimentology – lead them to believe that Moeritherium was semi-aquatic.

We already know that their closest relatives are the sirenians, or manatees and dugongs, which are fully aquatic. Researchers hope to look at other ancestors of elephants to find when they split off from sirenians and when they started feeding on land.

Evolutionary and phylogenetic trees

Casey Luskin seems to be stepping into Michael Behe’s clown shoes to perpetrate another round of “scientific analysis” based on inaccuracies. The Non-discovery blog analyzes why Luskin is wrong: Molecular evolution, retroviral evolution, and standard phylogeny give similar trees: “Why we know the tree is real.”

Hat tip to ERV: “Bort grows ERV and CytB trees!“

Human origin pinpointed

Robert Park wrote in What’s New:

The discovery in 2003 by Tim White of UC Berkeley of a 160,000 year old partial skeleton of Homo sapiens in Ethiopia was the strongest evidence yet that we did indeed come out of Africa.

A young molecular anthropologist at the University of Maryland, Sarah Tishkoff, saw that the mapping of the human genome provides a new tool for tracking the out-of-Africa migration of Homo sapiens: footprints in the DNA of living humans.

Now at the Univ. of Pennsylvania, Tishkoff’ s team, which included linguists as well as geneticists, narrowed the origin of modern humans to the inhospitable borderland between Angola and Namibia. Their study, published yesterday in Science, took researchers into remote regions to sample the bloodline of more than 100 distinct populations.

The exit point was in Northeast Africa at about the midpoint of the Red Sea.

You can read about her project here.

“Slavery makes my blood boil,” said Darwin

Charles Darwin was interested in the wonders of nature and how they came about; but he had another great passion, and that was a hatred of slavery.

“Darwin’s Sacred Cause” points out that Darwin married into an abolitionist family and that the notion of common descent, even before he published his theory of how it might happen, was an abolitionist’s plea for equal treatment of all men and women.

As usual, “the BBC has the story: ” Darwin’s twin track: evolution and emancipation.”

“It makes one’s blood boil,” said Charles Darwin.

Not much outraged the gentle recluse, but the horrors of slavery could cost him a night’s sleep.

He was thinking of the whipped house boy and the thumbscrews used by old ladies in South America, atrocities he had witnessed on the Beagle voyage.

Handy-dandy torture device

The screams stayed with him for life, but how much did they influence his life’s work?

…new evidence suggests that Darwin’s unique approach to evolution – relating all races and species by “common descent” – could have been fostered by his anti-slavery beliefs.

The notion of evolution had been bruited about for some time—at least seventy years—but no one had a mechanism for how it happened.

Why was Darwin’s evolution uniquely defined by common descent, the joining of races and species through shared ancestry? Darwin’s common descent image is so obvious today that we forget to question where it came from.

"Am I not a man and a brother?"

Common descent in Darwin’s younger day was ubiquitous in anti-slavery tracts. Consider the words of the famous cameo, depicting a kneeling slave asking “Am I Not a Man and a Brother?” That cameo was in fact the brainchild of the pottery-dynasty founder, Josiah Wedgwood, Darwin’s grandfather.

New evidence shows how indebted Darwin was to this anti-slavery heritage.

Darwin’s uncle Jos Wedgwood sold the firm’s London showroom, and ploughed the proceeds into an anti-slavery society, and in the 1850s (with American slavery still flourishing) the Wedgwoods continued using labels showing the slave under Britannia’s banner, which read “God Hath Made of One Blood All Nations of Men”.

The anti-slavery agitator Thomas Clarkson – the man who rode 35,000 miles collecting statistics in the sea ports on the evil trade – was another bankrolled by Josiah Wedgwood.

With a Wedgwood wife and mother, Darwin saw abolition as a “sacred cause” too, and in his culminating work, the Descent of Man (1871), he placed Clarkson at the moral apex of humanity and called slavery a “great sin”.

Darwin’s theory undermined the great moral excuse for slavery: that slaves belonged to a separate species.

In addition, Darwin was horrified by the torture that he saw when he visited slave-holding nations. (Britain had abolished slavery in the Great Reform Acto of 1832.) He saw the grief and fear of parents whose owners threatened to sell their children away from them. Ah, the traditional American family!

Transitional seal fossil

A major transitional fossil has been found. It’s a seal ancestor, 23 million years old. It a walking seal that looks a bit like an otter.

Puijila darwini

This is the oldest fossil of an ancestor to seals that has been found. Pujilla means “young sea mammal” in the Inuktitut language as spoken near where the fossil was found, on Devon Island. The species name darwini honours Charles Darwin. The great biologist hypothesized that land mammals would be likely to adapt to fresh water first and only later take to the sea. Pujilla, found in sediments laid down in a fresh water environment, is evidence for that hypothesis.

“The find suggests that pinnipeds went through a fresh water phase in their evolution,” said Natalia Rybczynski from the Canadian Museum of Nature (CMN) in Ottawa, who led the fieldwork.Pinnipeds are the seals, sea lions, and walruses. (Manatees returned to the water in a separate adaptation.)

“It also provides us with a glimpse of what pinnipeds looked like before they had flippers.”

The skeleton was about 65% complete, which enabled the researchers to reconstruct what the animal would have looked like in remarkable detail.

The legs suggest it would have walked upright on land; but the foot bones hint strongly at webbed feet.

The fossil was found in a former crater lake. Scientists have also found fossil fish from the same period, which may have been prey for the semi-aquatic seal.

“The remarkably preserved skeleton of Puijila had heavy limbs, indicative of well developed muscles, and flattened phalanges (finger or toe bones) which suggest that the feet were webbed – but not flippers,” said Mary Dawson from the Carnegie Museum of Natural History in Pittsburgh, US, another of the scientists.

The teeth indicate that the animal was a carnivore.

Until now, the most primitive fossil pinniped was a creature called Enaliarctos that dates from about the same period and appears to have lived in the sea along the northwestern coasts of North America.

Enaliarctos had flippers, but may have had to bring its prey to the shore for eating, whereas modern pinnipeds manage it at sea.

Intriguingly, different species of present-day seal swim in different ways – either rotating their flippers, or waving their hind-quarters from side to side, using the hind limbs for propulsion.

Enaliarctos appears to have been capable of both modes of swimming – and as a four-legged animal with four webbed feet, Puijila is a logical fore-runner of this creature which could swim with all four limbs.

This discovery suggests that seals, sea lions, and walruses evolved in the Arctic, and northern Canada and northern Russia likely places to look for more ancestral seals.

Brian Switek at Laelaps has detailed information from the actual paper in Nature.