Dispatches from the front-lines of evolutionary biology


When you visit new and unfamiliar territory it does not make much difference whether you are an anthropologist, a biologist or simply a tourist. It is always easy to describe in detail all the differences that you observe. Yet truly experienced travelers do know that in the end it is perhaps more interesting to discover what we have in common with those other people we encounter in foreign places rather than what we find different.

Now let us take this thought one step further. When we explore natural ecosystems we soon realize that what is alive in any particular environment not only interacts with all others but also shares characteristics with them. That is why we call the science biology. The sub-field that is concerned with the study of how organisms evolve through natural selection is called evolutionary biology.

This week we stumbled on two separate articles that described exciting new discoveries in this field. They give insight in the evolutionary processes that have produced the enormous biodiversity on the planet and also provide further proof of how directly we are related to all other life on Earth.The first article reports on the results of research conducted at Yale, Berkeley and Stanford, jointly published in the scientific journal Nature on Aug. 28th. The researchers compared data from the human genome to those of the fruit fly and the roundworm, and found distinct arrangements in the genetic architecture that were shared by all three species, particularly for genes that control reproduction and development. As Mark Gerstein, Professor of Biomedical Informatics at Yale University, the lead author on one of the papers pointed out: “The special thing about the worm and fly is that they are very distant from humans evolutionarily, so finding something conserved across all three -human, fly and worm – tells us it is a very ancient, fundamental process.”

The second article reports on an experiment that was conceived and executed by Emily Standen, who specializes in evolutionary biomechanics at McGill University in Ottawa. The study involved research into the question what could have generated the evolutionary transition from fish to animals that walked on land.

The fossil record has shown that about four hundred million years ago the first fish species started exploring land and evolved into four-limbed vertebrates, today’s amphibians, reptiles, birds, and mammals. One intermediate step in that evolutionary transition from water to land may have been marked by the so-called ‘Tiktaalik roseae’. This was a fish that resembled a crocodile and lived 417-354 million years ago. Well-preserved fossils of this animal were found in 2004 on Ellesmere Island in the Nunavut Territory of Canada, which is 600 miles above the Arctic Circle but was a subtropical marsh at the time, 400 million years ago. Tiktaalik was a true transitory animal and the paleontology experts were able to determine that it could breathe using a combination of gills and lungs.

The research team at McGill University carried out an experiment on a group of Polypterus, a type of freshwater fish that live in various areas in Africa. These remarkable fish also have a set of lungs alongside functioning gills, and can even crawl across land. They are considered the closest living relatives to the predecessors of the four legged tetra-pods.The researchers raised about a hundred juvenile fish permanently on land in only a millimeter of water for nearly a year with the purpose to study if, and how, they would adapt to the terrestrial environment. A control group was raised in a standard aquarium. In less than a year, they found that the fish that were raised on land showed significant anatomical and behavioral changes. They learned to raise their heads higher and more securely plant their fins on the ground. Their bone structure was even seen to change over time, with shoulder blades growing slightly longer than average and what appeared to be the slow development of a neck.



In the words of Darwin:
“We must, however, acknowledge, as it seems to me, that man with all his noble qualities… still bears in his bodily frame the indelible stamp of his lowly origin.”

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