Evolution: Horses, speciation and environment (Evolution)

by David Turell , Friday, February 10, 2017, 15:11 (2632 days ago) @ David Turell
edited by David Turell, Friday, February 10, 2017, 15:32

Which came first, speciation or environmental changes requiring adaptation? Environmental changes!

https://cosmosmagazine.com/biology/horse-study-reins-in-evolutionary-orthodoxy?utm_sour...

"The history of the horse family may hold the key to one of evolution’s classic conundrums: what comes first, new traits or a new environment?

"In the journal Science, Juan Cantalapiedra from the Humboldt Museum in Germany and colleagues in Spain and Argentina present evidence for the latter.

"They studied the body size and tooth morphology of 138 species of horses, all but six of them extinct, with the oldest dating from 18 million years ago, along with the rate at which the horse lineages diverged into separate species.

"They found that migration patterns and changes in environment drove the development of new traits. This is the opposite of the prevailing theory of evolution, which holds that new traits – such as bigger teeth or a thicker pelt – develop first, allowing species to then move into new environmental niches.

"Using fossils to gauge the body and teeth size of the specimens gave the researchers clues to the kinds of food the horses ate. Longer teeth and bigger body size, for instance, hinted that new grub was on the menu.

***

"They found that speciation bursts – comparatively rapid branch-splitting, resulting in multiple new species – did not correlate with the physical changes that were taking place in the animals at the time.

"This suggests strongly that evolution was driven by “extrinsic factors – such as geographical dispersals, increased productivity, or habitat heterogeneity – that release diversity limits and promote speciation”, they write.

"In other words, new traits and new species evolved because environmental changes allowed greater genetic diversification. This contradicts the idea of “adaptive radiation”, which holds that the evolution of new traits allowed species to move into previously unoccupied environments.

***

"None of the early stage speciation spikes were associated with a burst in body size or change of tooth structure. In fact, branches of the horse family that underwent fast speciation actually showed slower rates of tooth evolution.

"So how was speciation occurring without notable physical changes in these horses? A possible explanation is what the horses ate changed before physiological adaptions caught up.

“'We’d always thought you can only really become species-rich by adapting to new environments, but here it seems that the new species comes first, and then the anatomy changes later,” comments evolutionary biologist Alistair Evans from Monash University in Australia, who was not involved in the research.

"But, Evans adds, “there is much more to a species than just how big it is [and] how big its teeth are”.

"The complex evolutionary history of horses is far from being a closed case, with research in the area continuing to grow."

Comment: This finding seems logical to me. Move to a new area with better food and then adapt to the other environmental issues. Epigenetics play a role. However the varieties are all still horses and can interbreed. see below:

Another view: https://wattsupwiththat.com/2017/02/10/claim-climate-change-made-the-
modern-horse-of-course/

"Changing environments and ecosystems were driving the evolution of horses over the past 20 million years. This is the main conclusion of a new study published in Science by a team of palaeontologists from Spain and Argentina. The team analysed 140 species of horses, most of them extinct, synthesising decades of research on the fossil history of this popular group of mammals.

"According to the new results, these evolutionary changes could have been much slower than previously assumed. In fact, Cantalapiedra and colleagues were able to show that all these newly evolved species of horses were ecologically very similar. Thus, rather than a multiplication of ecological roles, the new results point to external factors, such as increasing environmental heterogeneity, as the main evolutionary force."