Our inner fish and other evolution fun facts

Even though I am not a biologist, I find evolution to be an endlessly intriguing subject, constantly throwing up intriguing new facts. Here are some recent items that caught my eye.

Stephen Colbert has a fascinating interview with evolutionary biologist Neil Shubin, discoverer of the fish-land animal transitional fossil Tiktaalik, about how much of our human biology came from fish. In his 2008 book Your Inner Fish: A Journey Into the 3.5 Billion-Year History of the Human Body, Shubin points out that although superficially we may look very different, many of our human features can be found in to have analogous forms in fish and thus probably existed from the time that we shared common fish-like ancestors with them. (Incidentally, Shubin was one of the expert witnesses in the Dover intelligent design trial in which he discussed the theory of evolution and the role that Tiktaalik played in clarifying the link between fish and land animals.)

For me, one of the most surprising things in learning about evolution was that whales, dolphins, and porpoises evolved from land mammals that returned to the sea from which their own ancestors had emerged. In fact, hippos are the animals most closely related to modern day whales.

Researchers have now discovered in the Kashmir region the fossils of a land-based ancestor to whales, dolphins, and porpoises. The fox-sized Indohyus, as it has been called, lived 48 million years ago and is an even closer relative to the whales than hippos, and sheds more light on how whales cam to be.

“The new model is that initially they were small deer-like animals that took to the water to avoid predators,” Professor Thewissen told BBC News. “Then they started living in water, and then they switched their diet to become carnivores.”

And then there was the New Scientist report last week of the discovery of a two million year old Uruguayan fossil of a rodent (Josephoartigasia monesi) that weighed about a thousand kilograms, which makes it the world’s largest rodent, about the size of a large bull. Of course, this species of giant rodent is extinct. The largest rodents now are the capybara, also found in South America, which clock in at a mere 50 kilos.

In reading the report, I discovered something else that I had not known, that North and South America had once split apart, and that this may explain how the giant rodent came into being. Later the huge landmasses joined again, causing the extinction.

South America saw a huge explosion in the diversity of rodents after the continent split from North America and became an island some 65 million years ago. Dinosaurs had just been wiped out and many animal groups were filling the void they left behind.

Without competition from other mammals which were diversifying on the other side of the water in North America, rodents of all sizes emerged in South America.
. . .
Around the time that the recently discovered J. monesi was alive, the two Americas were joined once more.

Sánchez speculates that the connecting land bridge may have helped bring about the demise of the giant rodents. Animals, among them the sabre-toothed cat, crossed the bridge in both directions bringing diseases, and competition for food and territory.

It is likely that changes in the climate will have also rendered the rodents’ home less hospitable. J. monesi was found in what is now an arid region, but was then lush and forested.

“Our work suggests that 4 million years ago in South America, ‘mice’ that were larger than bulls lived with terror birds, sabre-toothed cats, ground sloths, and giant armoured mammals,” say the Uruguayan researchers.

Of course, these explanations for the rise and fall of the giant rat are speculative and need to be corroborated with further research.

This is what I love about science: the constant discovery of exciting new findings, the challenge of fitting them into a theoretical framework while maintaining consistency with other scientific theories. All these things stimulate new research and ideas.

POST SCRIPT: Scott Ritter and Edward Peck

Scott Ritter is the US Marine who was a member of Hans Blix UN team that searched Iraq for WMDs prior to the invasion. He concluded that Iraq did not have any and repeatedly said so. For being correct, he was vilified by those anxious to go to war and almost completely banished from the media while those who were wrong on everything are still there, now pushing for war with Iran.

Scott Ritter and Edward Peck (former chief of mission for the US in Iraq) will speak tomorrow (Thursday) at at 7:30 pm at Trinity Cathedral in Cleveland. They have returned from a fact-finding mission in Iran.

Suggested donation: $10 general, $5 students. Trinity Cathedral is at 2230 Euclid Ave., across from CSU. Free parking is available in the Trinity Cathedral lot: entrance on Prospect Ave at E. 22nd.