Life Science Blog

In the Case of the Musk Ox Decline, Man is Not Guilty

Genetic evidence shows environment, not humans, killed off Arctic beasts

March 10, 2010

Ladies and Gentlemen of the Jury:

In the courtroom of natural history, it’s easy to point the finger of guilt at the usual suspect: man. Our bad rep is well founded — we’ve destroyed rainforests and wetlands, spewed pollutants into our waterways, and pumped our atmosphere full of greenhouse gases.

But now, we might find a small shred of redemption in an unlikely place: the ancient DNA of the musk ox.

Scientists examining the genetic diversity of ancient musk oxen have found that the decline in musk ox populations 12,000 years ago was not due to over-hunting by ancient humans, as some scientists have hypothesized. Rather, environmental change is a more likely reason for the population decline.

Musk oxen are large, shaggy relatives of sheep and goats that were once found all over the Arctic. But, along with other large mammals like mammoths and saber-toothed cats, their numbers began to dwindle in the late Pleistocene era.  While they did not die out completely, they did eventually disappear from Europe and Eurasia.  Today, most of the remaining 80,000 to 125,000 musk oxen are confined to Greenland.

To better understand the decline, researchers extracted DNA from musk ox bone, tooth, and horn samples that had been trapped in the Arctic ice at different points in time. They then compared the genetic sequences to determine how genetically diverse musk ox populations were at different points in history. According to the researchers, genetic diversity is a good indication of population size — the more diverse the population, the larger it probably was.

The results of the study, published in the March 8 early edition of Proceedings of the National Academy of Sciences, show that musk oxen populations have actually grown and shrunk a number of times over the past 60,000 years, and none of these declines correspond with known human migrations into musk ox territory. In fact, both man and musk oxen expanded into Greenland at about the same time. On the other hand, many of the declines coincided with extreme ecological changes, indicating that climate, not man, might be the cause.

That doesn’t mean we humans have communed peacefully with the gentle musk ox throughout history. Piles of musk ox bones associated with ancient human cultures in the Arctic indicate the contrary. But did we drive these noble beasts almost to extinction?  Ladies and gentlemen, I believe the DNA evidence speaks for itself.

About the Author

Anna Rothschild

Anna Rothschild is a producer and science writer from New York City. After graduating from Brown University with a degree in biology, she worked as a scientist at the American Museum of Natural History where she cloned humpback whale genes into bacteria, lassoed lizards in Floridian forests, and detected fraud in the caviar trade. Now, she reports on everything from life science, to space, to urban legends.


1 Comment

Might be nice to know how long musk oxen have been around. Last 60,000 years might just be a sliver of their evolutionary past…though that might be when humans have been lurking around. Or is it the case that samples cannot be found from older times?

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