Ancient Horse Mother Found

1 02 2012

A team of geneticists, paleontologists, and archaeologists have identified the ancient mother of all the horses alive today, according to a paper (link here) published in the Proceedings of the National Academy of Sciences, January 30.

The study, led by Alessandro Achilli, of the Dipartimento di Biologia Cellulare e Ambientale, at the Università di Perugia, in Perugia, Italy, determined that the common ancestral mare to all living horses trotted the earth between 130,000 and 160,000 years ago, with a date of approximately 140,000 years being most likely.  More importantly, the study also identified 18 major clusters of genes called haplogroups, that were involved in the domestication of horses.

Torroni and his colleagues examined 83 modern horse genomes from the Americas, Asia, Europe, and the Middle East.  While the generalities of horse domestication are broadly understood, the specifics of time and location are not.  This study sheds significant light on these aspects of the horse’s natural history.

The study indicates that horses were domesticated over a broad area of Eurasia with multiple incidents of domestication occurring at different times.  This differs from many other domestic animals, such as cattle and sheep, which were domesticated from a handful of animals at very specific locations and then spread through trade and capture.  At least one of these domestication events took place in Europe, with Iberia being a possible location for it.

Horses have an extended and close relationship with humans.  They have played a major role in human history.  Horses were widely used in warfare until the end of World War I, and were still used to some extent even in World War II.  In civilian use, millions of horses were engaged for transportation and to haul goods until the 1920s, when they were largely replaced by trucks and automobiles.  They were still a common sight on many American roads until the 1940s.

In addition to its general scientific interest, the paper points out that the results of the study can also be used to classify fossil horse remains, identifying where they belong on the horse family tree; better define and understand modern horse breeds and their ancestry; and evaluate the role of maternal ancestry in racehorse performance.

Bhimbetka_Rock_Paintng_Man_Riding_Horse

A 30,000 year old rock painting from Bhimbetka in north central India, showing a man riding a horse. This image comes from Wiki Commons and is used under the GNU Free Documentation License





Scientists use Mitochondrial DNA to Identify Recently Diverged Mouse Lemur Lineages

5 04 2010
This image is copyrighted under the creative commons attribution license by Weisrock D.W., Rasoloarison R.M., Fiorentino I., Ralison J.M., Goodman S.M., et al. (2010) for the article “Delimiting Species without Nuclear Monophyly in Madagascar's Mouse Lemurs”. Appearing in PLoS ONE 5(3): e9883. doi:10.1371/journal.pone.0009883.

The island of Madagascar, showing the areas of sampling used in this study.

An international team of researchers has used mitochondrial DNA (mtDNA) to help distinguish between a group of Madagascar Mouse Lemurs who have recently begun to diverge.

One of the issues associated with delineating species that have recently diverged from common ancestors is that often there has not been sufficient time for the usual cues of speciation, such as morphological differences, reproductive isolation, and monophyly within the gene tree to have become settled and readily evident.  Writing in the online journal, PLoS One, seven scientists from the United States, Germany, and Madagascar used multiple lines of evidence from mtDNA and nuclear DNA (nDNA) to identify “cryptically diverged” population-level mouse lemur lineages from throughout Madagascar.  It is believed to represent the most thorough sample of mouse lemur species ever conducted.

The result was the identification of a large number of geographically-defined clades.  These were strongly supported by the initial mtDNA evidence, as well as additionally supported by nDNA patterns.  The clades thus identified, are also supported by population divergence estimates based on genealogical exclusivity estimates.  The paper concludes that “Mouse lemur lineage diversity is reflected in both a geographically fine-scaled pattern of population divergence within established and geographically widespread taxa, as well as newly resolved patterns of micro-endemism revealed through expanded field sampling into previously poorly and well-sampled regions.”

For more information, please see the original article at the following URL: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009883





Researchers Use DNA to Find New Human Species… Probably

24 03 2010

In a report published Wednesday in the journal Nature, Russian scientists report using mitochondrial DNA (mtDNA) to identify a new species.  While the identification is tentative, and awaits confirmation, it none-the-less represents an important new use of DNA technology.

The discovery occurred in the summer of 2008, when the scientists were digging in Denisova cave, in Siberia.  They were looking for the remains and artifacts of Neanderthals, who occupied the cave between 30,000 and 48,000 years ago.  During excavations, they found a small sliver of finger bone.  According to the scientists, it was considered unremarkable at the time.

However, when they sent it to German scientists to have the DNA extracted and sequenced, they were in for a surprise.  The results did not match Neanderthals.  Nor did it match modern humans, who were also living in the area at the time.

The conclusion was that the bone represented a here-to-fore unknown human species.  Based on the differences between the bone’s DNA and that of modern humans, it is estimated that the species diverged from human ancestors a million years ago, long before the split between modern humans and Neanderthals.  By inference, this means that the proposed species left Africa in a previously unknown migration, sometime between that of Homo erectus about 1.9 million years ago and that of the Neanderthal ancestor Homo heidelbergensis, 300,000 to 500,000 years ago.

But, as yet, none of this is entirely certain.  The use of mtDNA poses its own problems, and scientists also must examine the bone’s nuclear DNA to get a full picture.  While mtDNA comes through the mother’s lineage, nuclear DNA comes from through the father’s.  It is important to have both in order to make a proper assessment.

Researchers point out that it is possible that some modern humans or Neanderthals living in Siberia 40,000 years ago had unusual mtDNA.  Only by also examining the nuclear DNA will a complete enough picture of the person it belonged to come out, allowing scientists to make a determination.  Such a picture might also allow scientists to properly define this new relative’s position within the human family tree.

To read more about this find, please see the article in Nature News at the following URL:  http://www.nature.com/news/2010/100324/full/464472a.html.