Friday, 24 June 2016

Mudskippers Defy Darwinian Dogma of Transition from Water to Land

Mudskippers will dry out if they’ll adopt a terrestrial lifestyle. Image courtesy of H. Krisp, Creative Commons (CC BY 3.0).

Joel Kontinen

New research proposes that sea animals might have “evolved the ability to live on land many times,” as a report posted on Science Daily puts it.

This challenges “the perception that this extreme lifestyle shift was likely to have been a rare occurrence in ancient times. New research shows 33 different families of fish have at least one species that demonstrates some terrestrial activity and, in many cases, these behaviors are likely to have evolved independently in the different families.”

This Darwinian optimism might be uncalled for, however:

Convergent evolution has for ages been the standard Darwinian method for explaining away features shared by unrelated species, such as echolocation in bats and dolphins.

However, the transition from land to sea – another Darwinian dogma associated with the jump from sea to land – is likewise fraught with difficulties. Mathematician and philosopher David Berlinski calculates that a cow-like creature living on dry land would have needed at least 50, 000 morphological changes for such a move. From skin to the breathing apparatus, almost everything has to be changed if the cow wants to stay alive in its new watery environment. Like transforming a car into a submarine, it needs an enormous amount of changes.

Moreover, Tiktaalik, once assumed to be the earliest terrestrial creature, has lost its iconic status, as land animals predate it by several million years according to the evolutionary timescale.

Now, evolutionary ecologist Dr Terry Ord, an evolutionary ecologist at the University of New South Wales and a co-author of a new paper published in the journal Evolution, acknowledges that the real threat for sea animals trying to settle on land is drying out:

"The real difficulty in developing a fully-fledged terrestrial lifestyle may be in preventing drying out. This has direct consequences for them breathing on land because they still require their gills, which need to stay moist to function properly."

Mudskippers can jump onto land but if they won’t return to the sea, they will eventually dry out. They are not designed to be terrestrial creatures.

Darwinian stories tend to be entertaining but often a bit fishy.


University of New South Wales. 2016. Fish out of water are more common than thought. Science Daily. (22 June).