Missing link to the pinnipeds

From Nature magazine, via Scientific Blogging, news of a missing link in the fossil record of the evolution of pinnipeds: Puijila Darwini - 'Missing Link' In Evolution Of Seals, Sea Lions And Walruses.

Modern seals, sea lions, and walruses all have flippers—limb adaptations for swimming in water. These adaptations evolved over time, as some terrestrial animals moved to a semi-aquatic lifestyle. Until now, the morphological evidence for this transition from land to water was weak.


Skeletal illustration of Puijila darwini. Credit: Mark A. Klingler/Carnegie
Museum of Natural History

"The remarkably preserved skeleton of Puijila had heavy limbs, indicative of well developed muscles, and flattened phalanges which suggests that the feet were webbed, but not flippers. This animal was likely adept at both swimming and walking on land. For swimming it paddled with both front and hind limbs. Puijila is the evolutionary evidence we have been lacking for so long," says Mary Dawson, curator emeritus of Carnegie Museum of Natural History.

Portions of the Puijila darwini specimen were found in 2007 in deposits that accumulated in what was a crater lake in coastal Devon Island, Nunavut, Canada. A subsequent visit in 2008 yielded the basicranium, an important structure for determining taxonomic relationships.

Speaking of evolution...

New research at the University of Chicago suggests that fish possessed the genes necessary to develop legs and feet well before environmental conditions caused those genes to be expressed:

A long-held theory of the development of limbs is overturned by a study that shows the molecular wherewithal to make hands and feet was present long before the first fish took the momentous step on to land.

Animals with limbs - tetrapods - first came onto the scene about 365 million years ago. However, fish already possessed the pattern of gene activity associated with helping to grow hands and feet which was present in them at least 400 million years ago, according to research at the University of Chicago.

“We found that the genetic capability seen in tetrapods to build limbs is present in even more primitive fish,” said lead author Marcus Davis, a postdoctoral fellow in Prof Neil Shubin’s lab at the University of Chicago.

This suggests a very interesting thought. The traditional theory of evolution by mutation filtered by natural selection implies that genetic variations take hold in populations in response to selection pressures, where the mutations accord individuals with advantages in survival and/or reproduction. Why would fish need a genetic predisposition to form legs and feet if they had no environmental selection pressure to do so?

Well...

... what if an Intelligent Designer decided to "salt in" some interesting genes -- you know, to sort of guide the path of evolution in a particular direction?

Not sayin' it was Jehovah, or the Flying Spaghetti Monster, or any particular deity or entity. I'm just sayin', is all.

Care to comment, Mr Dawkins?