You are what you poop

Not the most delicate way to put it, but true, as some paleontological sleuthing shows...

Scientists went prospecting along Alaska’s Yukon River, not for gold, but for soil samples in the permafrost looking for DNA from the urine and feces of ice-age mammals.

They struck it rich, and identified DNA from mammoth, bison, moose, horse, and snow shoe hare. The mammoth and horse DNA came from sedimentary layers about 10,000 years old—that is more recent than the youngest known fossil bones of these animals by at least 300 years.

The permafrost DNA implies that these species survived longer than originally presumed on the basis of the skeletal fossil remains, and indicates that the ice-age extinction of large mammals in North America was not a sudden event as previously thought.

Photo credit and more info: http://www.physorg.com/news180095166.html

Whither Jurassic Park?

So will the science of Jurassic Park remain within the realm of fiction, or will someday genetically engineered mammoths, dinosaurs, and trilobites again roam the Earth?

It is unscientific to use terms like “never” except in cases where the realization of a phenomenon would require violation of physical laws of nature, and in paleontology paradigms are often overturned by the discovery of a single, fortuitous fossil, so especially in paleontology is it unwise to use the term.

Michael Crichton’s books were best sellers because they were plausible science fiction—as were Jules Verne’s and Arthur C. Clarke’s imaginings of the future. Some of their visions have been realized, others have not. It is the “possibility of the possible” that attracts writers to science fiction, and scientists to science.

Photo credit: http://www.3dscience.com

S'moa DNA

Scientists from Down Under have extracted DNA from feathers of the extinct moa, the 2.5 meter tall birds that dominated New Zealand’s terrestrial ecosystems until the arrival of humans and non-native mammals about 700 years ago.

Previously, DNA had been extracted from the feathers of modern birds and from museum specimens of birds that have gone extinct in historical time, and only from the base or quill end of the feathers.

The moa study showed that viable DNA could be obtained from older, subfossil feathers and from the distal end of the feather, the rachis and barbs. Scientists are not seeking to use the DNA to clone the moa, but to identify the species of moa that they come from.

The success with moa feathers demonstrates that useful information can be obtained from subfossil feathers and from parts of feathers not previously considered useful in genetic analysis.

Reference: Nicolas J. Rawlence, Jamie R. Wood, Kyle N. Armstrong, and Alan Cooper, 2009, DNA content and distribution in ancient feathers and potential to reconstruct the plumage of extinct avian taxa. Proceedings of the Royal Society, B, October 7, 2009 276:3395-3402; published online before print July 1, 2009, doi:10.1098/rspb.2009.0755

Photo credit: Extinct Monsters by Rev. H. N. Hutchinson, illustrations by Joseph Smit (1836-1929) and others. 4th ed., 1896. Plate XXIII between pages 232 and 233.

DNA dream time

So how close are scientists to being able to clone a now-extinct species?

Ideally, scientists would start with a species that has recently gone extinct, and one for which we have tissue samples. Australia’s extinct Tasmanian tiger fits these criteria. The last-known captive animal died in 1936.

A team of scientists have inserted part of a bone-making gene from the Tasmanian tiger into a mouse embryo and found that it functioned properly. This marked the first time that DNA from an extinct species successfully induced a functional response in another living organism.

However, scientists are not making plans to exhibit a cloned Tasmanian tiger anytime soon. Through a gene-by-gene study scientists can hope to learn the functions of the genes from extinct species, but assembling an entire animal from fossil genetic material is still the realm of science fiction.

Reference: Pask, A. Behringer, R.R., and Renfree, M., 2008. Resurrection of DNA function In Vivo from an extinct genome. PloS One 3(5)

Photo credit: http://dsc.discovery.com/news/2008/05/20/gallery/tasmanian-tiger-540x380.jpg

DNA from Museum drawers

Scientists have recovered DNA from mammoth hair that had been stored in a drawer at room temperature for the 200 years since the 1799 discovery of a naturally mummified mammoth.

This discovery raises the prospect of sequencing DNA from the hair and feathers of other specimens from museum drawers.

We are still far from cloning extinct organisms from preserved DNA, and a Jurassic Park scenario is still science fiction, but these discoveries, while controversial, have established a new discipline, creating lab standards and research protocol for rigorous and repeatable results.

The information from fossil DNA helps to clarify the relationships between extinct animals and their living descendants.

Reference: Penn State University Webb Miller. Science, 317 (5846), 1927 (Sept. 28, 2007)

Photo credit: Stephan Schuster Lab, Penn State

Oldest DNA

Fossil DNA hunting is a recent phenomenon, as it was long assumed that the molecules could not survive the vagaries of time and preservation to become fossils.

The current claim for oldest preserved DNA comes from 419-million-year-old salt deposits from Canada. This is an amazing claim, as previous “oldest DNA” reports are from animals only tens of thousand years old.

Every claim of old DNA is subject to intense scrutiny and is accepted only after successful independent trials to replicate the results. The 419 million year old DNA is from salt-loving or halophilic bacteria, representatives of which are still around today and which provide a comparison for the fossil DNA sequences.

The discovery of halophiles gives encouragement to looking for microbes in other unusual places...like Mars. Click on today's title to learn more.

Reference: J.S. Park, et al.,, 2009, Geobiology 7 no. 5, p. 515-523, Haloarchaeal diversity in 23, 121 and 419 MYA salts