Showing posts with label evolution. Show all posts
Showing posts with label evolution. Show all posts

26 Nov 2011

First Dogs Came from East Asia/Genetic Study

Researchers at KTH say they have found further proof that the wolf ancestors of today’s domesticated dogs can be traced to southern East Asia — findings that run counter to theories placing the cradle of the canine line in the Middle East.

Dr Peter Savolainen, KTH researcher in evolutionary genetics, says a new study released Nov. 23 confirms that an Asian region south of the Yangtze River was the principal and probably sole region where wolves were domesticated by humans.

Data on genetics, morphology and behaviour show clearly that dogs are descended from wolves, but there’s never been scientific consensus on where in the world the domestication process began. “Our analysis of Y-chromosomal DNA now confirms that wolves were first domesticated in Asia south of Yangtze River — we call it the ASY region — in southern China or Southeast Asia”, Savolainen says.

The Y data supports previous evidence from mitochondrial DNA. “Taken together, the two studies provide very strong evidence that dogs originated in the ASY region”, Savolainen says.

Archaeological data and a genetic study recently published in Nature suggest that dogs originate from the Middle East. But Savolainen rejects that view. “Because none of these studies included samples from the ASY region, evidence from ASY has been overlooked,” he says.

Peter Savolainen and PhD student Mattias Oskarsson worked with Chinese colleagues to analyse DNA from male dogs around the world. Their study was published in the scientific journal Heredity.

Approximately half of the gene pool was universally shared everywhere in the world, while only the ASY region had the entire range of genetic diversity. “This shows that gene pools in all other regions of the world most probably originate from the ASY region”, Savolainen says.

“Our results confirm that Asia south of the Yangtze River was the most important — and probably the only — region for wolf domestication, and that a large number of wolves were domesticated”, says Savolainen.

In separate research published recently in Ecology and Evolution, Savolainen, PhD student Arman Ardalan and Iranian and Turkish scientists conducted a comprehensive study of mitochondrial DNA , with a particular focus on the Middle East. Because mitochondrial DNA is inherited only from the mother in most species, it is especially useful in studying evolutionary relationships.

“Since other studies have indicated that wolves were domesticated in the Middle East, we wanted to be sure nothing had been missed. We find no signs whatsoever that dogs originated there”, says Savolainen.

In their studies, the researchers also found minor genetic contributions from crossbreeding between dogs and wolves in other geographic regions, including the Middle East.

“This subsequent dog/wolf hybridisation contributed only modestly to the dog gene pool”, Savolainen explains.
 (SciLifeLab)
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24 Aug 2011

Science/ Top 10 Missing Links

Every few years scientists unearth the bones of humanity's forefathers. From Lucy to the Hobbits of Flores Island -- we are gradually seeing building the puzzle of mankind's evolution.
1 Neanderthal
Photo Credit: Mauro Cutrona
Stocky and squat and well suited for the cold, Neanderthals looked distinctly different from modern humans. But they were like us in other ways: they buried their dead, cared for their sick and injured and may have been capable of language and music. Scientists recently put together a complete Neanderthal skeleton and are working on the genome.
2 Cro-Magnon
Credit: public domain
These people looked identical to modern humans and lived in Europe between 35,000 and 10,000 years ago. Their cave paintings and sculptures are the earliest known examples of art by a prehistoric people.
3 Homo floresiensis
Credit: National Geographic Society/ Peter Schouten
It turns out those Floresians were actually on to something. For centuries, their mythology described a race of very small human-like creatures called the Ebu Gogo. Hardly anyone took them seriously, however, until 2003, when word broke that a new species of diminutive hominids was discovered on the Indonesian island.
4 Homo erectus
Credit: Wikimedia commons user Steveoc 86
For H. erectus, it may have paid to be dense. According to one theory, males rammed each other with their thick skulls in order to win females. H. erectus is generally believed to be the direct ancestor of modern humans and also the first hominid to live in caves and
5 Homo ergaster
Credit: Flickr user flowcomm
Scientists can't decide whether this African hominid is just a failed predecessor of H. erectus or the rightful ancestor of modern humans. It had a thinner skull than H. erectus and was more proficient at making tools and using fire.
6 Homo habilis
Credit: Wikimedia commons user Lillyundfreya
Many scientists believe H. habilis is the missing link between the ape-like hominids like Lucy and the more human-like ones that came after. It had long ape-like arms but walked on two feet and was capable of creating crude tools.
7 Paranthropus boisei
Credit: Wikimedia commons user Lillyundfreya
If P. boisei and its relatives weren’t such picky eaters, we might not be here to wonder about them. They split from the line leading to modern human some 2 million years ago and lived alongside our ancestors for millions of years, but died out after failing to adapt their diets.
8 Paranthropus aethiopicus
Credit: Guérin Nicolas
This early ape-like hominid walked on two legs and lived between 2.8 million and 2.2 million years ago. Based on skull measurements, scientists concluded this species had the smallest adult hominid brain ever discovered.
9 Australopithecus africanus
Credit: Flicker user flowcomm, Sterkfontein Caves
A. africanus was an early descendent of Lucy and lived in Southern Africa between 2 million and 3 million years ago. Its brain was larger than Lucy's and its facial features were more human-like.
10 Australopithecus afarensis
Credit: Wikimedia commons user 1997
The most famous member of this species is Lucy, an adult female skeleton discovered in 1974 and nicknamed after a Beatles song. Lucy lived about 3.18 million years ago and was fully capable of walking and running on two legs.



SOURCE- LIFESCIENCE.COM

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15 Jul 2011

SC/Monkeys and humans more closely related, new species disovery suggests

Humans and monkeys may have diverged more recently than scientists have thought, a partial primate skull discovered in Saudi Arabia suggests.

Our lineage might have diverged from our monkey relatives later than previously thought, a new primate fossil from Saudi Arabia now suggests.
A primate skull fragment discovered in Saudi Arabia suggests that the lineages of monkeys and humans split later than had been previously thought, indicating that Old World monkeys, such as this Japanese snow monkey.Newscom/File
One key step in understanding human evolution is pinning doing when the hominoid lineage, which includes apes and humans, diverged from the Old World monkeys.
"If we can refine our understanding of the date of split between hominoids and Old World monkeys and eventually get a better idea of what was happening with the ecology, climate and composition of co-occurring mammals at that time, we will learn about the conditions driving our own ultimate origins," researcher William Sanders, a paleontologist at the University of Michigan at Ann Arbor, told LiveScience.
Genetic analysis of humans, monkeys and other primates had placed the split at roughly 35 million to 30 million years ago, during the early Oligocene period. However, the fossil record from the mid-to-late Oligocene, some 30 million to 23 million years ago, had previously provided little evidence supporting the timing of the divergence.
Primate skull
Now researchers have revealed a partial skull roughly 29 million to 28 million years old of a previously unknown species of medium-sized primate that might have come on the scene just before our lineage split away from Old World monkeys.
When alive the primate likely resembled a New World monkey (a group that includes marmosets, tamarins, capuchins and other monkeys), sporting a tail and moving on all fours.
"It's not a monkey, it's not an ape — it's this intermediate, a precursor fossil for all apes and Old World monkeys," said researcher Iyad Zalmout, a paleontologist at the University of Michigan at Ann Arbor.
The fossil, unearthed in 2009 near the west coast of Saudi Arabia during a joint field expedition of the Saudi Geological Survey and University of Michigan, is dubbed Saadanius hijazensis. In Arabic, "saadan" collectively refers to apes and monkeys, while "Al Hijaz" refers to the region where the fossil was found.
The fossil had evidence of deep bite marks and possibly fatal puncture wounds on it. Back then, the area was a warm, lush forest very unlike most of present-day Saudi Arabia, and was populated by extinct mammals known as creodonts, carnivores generally more heavily built than living cats and canines that possessed large fangs capable of inflicting the damage seen in the new fossil skull.
Shared features
The fossil, which scientists said belonged to an adult male weighing about 33 to 44 pounds (15 to 20 kilograms), possessed features of the catarrhines, the common ancestor of hominoids and Old World monkeys, such as a tubular ectotympanic, a bone linked with the eardrum. These new findings hint the divergence between hominoids and Old World monkeys happened between 29 and 24 million years ago.
"Between 24 million and 29 million years ago, there's the beginning of the spreading of the Red Sea, and changes in temperature and sea level and climate, and new animals coming in from Europe and new vegetation from South Asia," Sanders said. "Now we can start looking at all these factors to better understand the evolutionary laboratory that drove the emergence of groups like our own."
Future research will focus on trying to find more of Saadanius, particularly the rest of the skeleton besides its skull.
"We'd like to know more about how it negotiated around the landscape," Sanders said.
The scientists detailed their findings in the July 15 issue of Nature.

Source: LiveScience
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