Extinct goat was cold-blooded

Nov 18, 2009 by Lin Edwards weblog
Extinct goat Myotragus balearicus. Image: Xavier Vázquez, via Wikipedia.

(PhysOrg.com) -- An extinct goat that lived on a barren Mediterranean island survived for millions of years by reducing in size and by becoming cold-blooded, which has never before been discovered in mammals.

The goat, Myotragus balearicus, lived on what is now Majorca, a Spanish island. The island had scarce resources, and there was no way for the goats to leave, and so scientists wondered how they had thrived for so long. A recently published research paper reveals the extinct goat survived by adjusting its growth rate and metabolism to suit the available food, becoming cold-blooded like reptiles.

Paleontologists studying fossilized Myotragus bones compared them to bones of reptiles living in the same region at the same time, and found surprising similarities. The bones of warm-blooded animals show uninterrupted fast growth, while the bones of cold-blooded animals have parallel growth lines showing interrupted growth corresponding to growth cycles, rather like the rings seen in tree trunks. Growth and metabolism rates are adjusted to suit the amount of food available, whereas warm-blooded animals require food to be available continuously. The Myotragus bones showed the same interrupted growth as reptiles.

Myotragus are the first mammals ever known to have achieved the same flexibility, and hence survivability, as reptiles. They also saved energy by having a brain half the size of hoofed mammals its own size, and its eyes were only a third of the size.

Skeleton of a Myotragus balearicus. Image: Francisco Valverde, via Wikipedia

The adult goats stood around 18 inches (45 cm) high, and the kids were around the size of a large rat. Reaching adulthood would have taken many years. Paleobiologist Meike Kohler of the Autonomous University of Barcelona, said the goats would have moved slowly to conserve energy, and probably spent a lot of time lying around basking in the sun. The postcranial skeleton suggested the could not jump, run or move fast, which made it easy prey.

Myotragus survived on the island as dwarf cold-blooded animals for millenia because they had no natural enemies, but they could not survive the predation of humans when they arrived on the island about 3,000 years ago. In total, the species inhabited the island for over five million years.

The paper was published online this week in the Proceedings of the National Academy of Sciences.

More information: Physiological and life history strategies of a fossil large mammal in a resource-limited environment, PNAS, Published online before print November 16, 2009, doi: 10.1073/pnas.0813385106

© 2009 PhysOrg.com

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User comments : 11

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Nov 18, 2009
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3.7 / 5 (7) Nov 18, 2009

Virtually every exposition of evolution lately makes the same stupid assumption: "survived by adjusting." WRONG.

Species do NOT change in order to survive. There can be no volition involved.

It's best put the way I learned it in the 10th grade: "Species do not change in order to survive; they survive because they change."
5 / 5 (6) Nov 18, 2009
@voiceofuruguay - "kid" is the technical term for a young goat.

*EDIT* I do agree that they would be really interesting to see today.
3.7 / 5 (3) Nov 18, 2009
Virtually every exposition of evolution lately makes the same stupid assumption: "survived by adjusting." WRONG.

"Species do not change in order to survive; they survive because they change."

That sort of sloppy language bugs me as well. But it seems that some people just can't manage to think in evolutionary terms. Part of the problem is the English language.

'the goats survived because they had mutations that enabled some of them to have a lower metabolic rate thus increasing those particular goats percentage of the gene pool' just doesn't flow of the tongue.

5 / 5 (3) Nov 18, 2009
OASA, humanist was 100% correct so why did you give him a one? How about you make your very first post to explain just what irked you in that post.

Life is not self-adjusting. It is shaped by the environment. The goats did not become cold blooded because they wanted to. The did so because those that didn't died out leaving the ones with the right mutations for the environment.

5 / 5 (2) Nov 18, 2009
Were there cavemen who stared at goats too?
not rated yet Nov 19, 2009
Individuals do not evolve. Populations evolve over time in response to various environmental stresses.
5 / 5 (2) Nov 19, 2009
Were there cavemen who stared at goats too?

Of course. Just how much staring and thinking had to go on before someone decided to milk a goat?

Will I get kicked in the head.
What will it taste like.
Do I really want to know.
Wouldn't it be better to just put an arrow through the smelly creature and be done with it.
Those horns are cool. I need a pair for the Lodge meeting.
My butt hurts from sitting here so long.
If I claim to be planning to milk the damn thing will my wife pretend that she believes I wasn't just sitting and staring off into the distance.
Bloody Hell, she believed me and now I have to milk the thing.

Now you have a better understanding how mankind progresses.

5 / 5 (1) Nov 19, 2009
Australian placental mammals, as well as the marsupial mammals have evolved to have reduced metabolic rates -in the case of several Australian rodents, they undergo daily "torpor" when they lower their body temperature, and rely on ambient heat to warm up. This goat has apparently gone one step further.
It will be interesting to see what Svante Paabo and other plaeogeneticists will make of the fossil genome. If the goat has been extinct for only three millennia, much of the genome will be retrievable.
1 / 5 (1) Nov 19, 2009
It would be interesting to read exactly how much less the goat needed food, compared to a "regular" animal of the same size.
Nov 19, 2009
This comment has been removed by a moderator.
1 / 5 (1) Nov 23, 2009
While interesting their conclusion rests on the assumption that cold blood is the only possible explanation for interrupted bone growth.
not rated yet Nov 23, 2009

Virtually every exposition of evolution lately makes the same stupid assumption: "survived by adjusting." WRONG.

Species do NOT change in order to survive. There can be no volition involved.

I have tried over the years to wake-up the pseudo-scientists behind this rather unscientific publication to the fact you mention. For some reason, probably a lack of intelligence, our efforts fail.. The only other possible reason would be 'lack of education'.. but the facts of our attempts negate that one.
They are trying to push science back to the Inquisition?

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