Caricature of evolution in discussion of Homo floresiensis

I was fascinated by the articles and the letter in Nature magazine that announced the discovery of a new species of human that survived until 12,000 years ago. Apparently, another branch of humans developed from Homo erectus hundreds of thousands of years ago and survived, isolated on Flores island in Indonesia. It has been named Homo floresiensis, after the island.

Like many populations isolated on islands, they could make their resources go farther by staying or becoming small. So developed a separate human species about 1 metre tall and “with a brain the size of a grapefruit.” Nevertheless, they were smart enough to make stone tools and to hunt the pygmy elephant and Komodo dragon. The previous new human species was Java Man, discovered 110 years ago.

However, I was annoyed by the comments made in our local newspaper, the Toronto Globe and Mail. Someone interviewed said that this discovery contradicted the scientific theory that humans somehow evolved in a steady, inevitable line. That is a rank misinterpretation of the theory. The true picture is one of branching and pruning, branching and pruning. I was moved to write this blog article as a reaction—and for that I needed a blog. Enter “Science Notes.”

It is only when a group is relatively unsuccessful — as in horses (family Equidae, 9 species), elephants (family Elephantidae, 2 species), and great apes (family Hominidae, 5 species) — that one can pick out a supposed “path to the top.”

Look at a successful group, such as Old World fruit-eating bats (Family Pteropodidae, 170 species), deer (family Bovidae, 137 species), or Old World monkeys (Cercopithecidae, 85 species), and you’ll see a hundred paths, all ending up with a different result.

Or look at fish. How could you elucidate one single path to the top for catfish?

Although the Mekong giant catfish may be the largest species of catfish, thousands of other species of catfish exist. According to John Lundberg, researcher with the All Catfish Species Inventory, 2,800 species of catfish have already been described and an additional 1,500 species may yet be discovered. “One out of every four freshwater fish, one out of ten fishes, and one out of twenty vertebrates…is a catfish.” Catfish are found on every continent except Antarctica and in fresh, coastal, and marine waters. They are perhaps the most ecologically and economically important group of fish in the world.— National Geographic

This diagram shows the Homo lineage through time and spread over different continents.

See also Science news of the year.

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