Science Friday: Primeval architects of Earth's O2 | Diet killed Gigantopithecus | Siberia: wildlife refuge of the last ice age

Meet the molecule responsible for giving Earth all of its oxygen

About 2.5 billion years ago, our planet had virtually no oxygen, and lifeforms were primitive. Then, oxygen levels suddenly spiked, the entire landscape of the planet changed, and we were on our way to complex life. Now, at last, we know why.

Earth probably wouldn't have gotten much past simple multi-cellular organisms without the Great Oxidation Event, let alone give rise to intelligent life. Aerobic organisms are able to harness far more energy than their anaerobic counterparts, and that means much more complex lifeforms can evolve than would otherwise be possible.

But there's a mystery here. Before the Great Oxidation Event 2.4 billion years ago, all organisms were naturally anaerobic. That doesn't just mean they couldn't use oxygen — the gas was actually toxic to them. And yet the only way to generate oxygen on a planetary scale was for organisms to release it as part of photosynthesis. That means anaerobic organisms effectively committed mass suicide to pave the way for their aerobic successors. Indeed, scientists suspect the Great Oxidation Event kicked off the first and most massive extinction event in our planet's history.

[...]

http://io9.com/5874963/meet-the-molecule-responsible-for-giving-earth-all-of-its-oxygen

Did Bigfoot Really Exist? How Gigantopithecus Became Extinct

Bigfoot. Sasquatch. Yeti. The Abominable Snowman. Whatever you want to call it, such a giant, mythical ape is not real—at least, not anymore. But more than a million years ago, an ape as big as a polar bear lived in South Asia, until going extinct 300,000 years ago.

Scientists first learned of Gigantopithecus in 1935, when Ralph von Koenigswald, a German paleoanthropologist, walked into a pharmacy in Hong Kong and found an unusually large primate molar for sale. Since then, researchers have collected hundreds of Gigantopithecus teeth and several jaws in China, Vietnam and India. Based on these fossils, it appears Gigantopithecus was closely related to modern orangutans and Sivapithecus, an ape that lived in Asia about 12 to 8 million years ago. With only dentition to go on, it’s hard to piece together what this animal was like. But based on comparisons with gorillas and other modern apes, researchers estimate Gigantopithecus stood more than 10 feet tall and weighed 1,200 pounds (at most, gorillas only weigh 400 pounds). Given their size, they probably lived on the ground, walking on their fists like modern orangutans.

Fortunately, fossil teeth do have a lot to say about an animal’s diet. And the teeth of Gigantopithecus also provide clues to why the ape disappeared.

The features of the dentition—large, flat molars, thick dental enamel, a deep, massive jaw—indicate Gigantopithecus probably ate tough, fibrous plants (similar to Paranthropus). More evidence came in 1990, when Russell Ciochon, a biological anthropologist at the University of Iowa, and colleagues (PDF) placed samples of the ape’s teeth under a scanning electron microscope to look for opal phytoliths, microscopic silica structures that form in plant cells. Based on the types of phyoliths the researchers found stuck to the teeth, they concluded Gigantopithecus had a mixed diet of fruits and seeds from the fig family Moraceae and some kind of grasses, probably bamboo. The combination of tough and sugary foods helps explain why so many of the giant ape’s teeth were riddled with cavities. And numerous pits on Gigantopithecus‘s teeth—a sign of incomplete dental development caused by malnuntrition or food shortages—corroborate the bamboo diet. Ciochon’s team noted bamboo species today periodically experience mass die-offs, which affect the health of pandas. The same thing could have happened to Gigantopithecus.

[...]

http://blogs.smithsonianmag.com/hominids/2012/01/did-bigfoot-really-exist-how-gigantopithecus-became-extinct/

Siberia was a wildlife refuge in the last ice age

10 January 2012 by Wendy Zukerman

SIBERIA, a name that conjures up images of snow and ice, may have been an unlikely refuge from the bitter cold of the last ice age. Ancient DNA from the region paints a picture of remarkably stable animal and plant life in the teeth of plunging temperatures. The findings could help predict how ecosystems will adapt to future climate change.

The permanently frozen soil of Siberia, Canada and Alaska preserves the DNA of prehistoric plants, fungi and animals. "It's a giant molecular freezer," says James Haile at Murdoch University in Perth, Western Australia.

Glacial ice can also contain ancient DNA but permafrost is much more abundant than ice and so should provide a more complete picture of the effects of prehistoric climate change, says Haile. Last month, at the International Barcode of Life Conference in Adelaide, South Australia, his colleague Eva Bellemain of the University of Oslo in Norway revealed the first fruits of their analysis of Siberian permafrost DNA.

The samples were extracted from 15,000 to 25,000-year-old frozen sediment in southern Chukotka in north-eastern Siberia. Their age is significant: around 20,000 years ago temperatures plummeted and ice sheets blanketed much of the northern hemisphere - but parts of Siberia, Canada and Alaska apparently stayed ice-free (Quaternary Science Reviews, DOI: 10.1016/j.quascirev.2011.07.020).

Fossils and pollen found in these regions suggest they may have acted as a refuge for plants and animals during this time, but Bellemain turned to fungal DNA to get a complete picture of the environment. Many fungi consume plants, and so indicate the plant life around at the time.

Using 23 permafrost cores, Bellemain identified around 40 fungal taxa that thrived during the last ice age. "We didn't expect to find so much," she says.

The diversity of fungi found suggests that a brimming plant community thrived in northern Siberia to support them. This range of plants should also have sustained a diverse assembly of mammals - and the samples indeed contain DNA from woolly rhinoceros (Coelodonta antiquitatis), woolly mammoths (Mammuthus primigenius), reindeer (Rangifer tarandus) and moose (Alces alces) dating back to between 15,000 and 25,000 years ago (Molecular Ecology, DOI: 10.1111/j.1365-294x.2011.05306.x).

[...]

http://www.newscientist.com/article/mg21328464.900-siberia-was-a-wildlife-refuge-in-the-last-ice-age.html