Monday, November 27, 2006

Spindle neurons: 30 million years in Cetaceans, 15 in primates

It's not often that a research results gives me goosebumps. This one did, since I'd completely missed that spindle neurons had previously been identified in the toothed whales (how the heck did I miss that?!). Emphases mine.
Humpback whale found to have 'human' brain cell - World - Times Online

Researchers in the US have discovered that humpback whales have a type of brain cell seen only in humans, the great apes, and other cetaceans such as dolphins.

Studying the brains of humpbacks, Patrick Hof and Estel Van der Gucht of the Department of Neuroscience at Mount Sinai School of Medicine in New York discovered a type of cell known as a spindle neuron in the cortex, in areas comparable to where they are seen in humans and great apes.

Although the function of spindle neurons is not well understood, they may be involved in processes of cognition - learning, remembering and recognising the world around oneself. The cells are also thought by some to be affected by Alzheimer’s disease and other debilitating brain disorders such as autism and schizophrenia.

The findings may help to explain some of the distinctive traits exhibited by whales, such as sophisticated communication skills, the ability to form alliances and co-operate, the researchers report in The Anatomical Record.

They say their study may subsequently indicate that such whales are more intelligent than they have been given credit for, and suggests that spindle neurons – the likely basis for complex brains - either evolved more than once, or have gone unused by most species of animals, kept only in those with the largest brains.

.... the spindle neurons found in humpback whales were discovered in the same location as toothed whales, suggesting that the cells may be related to brain size, reported Reuters.

Toothed whales, such as orcas, are generally considered more intelligent than baleen whales such as humpbacks and blue whales, which filter water for their food.

The humpback whales also had structures resembling 'islands' in the cerebral cortex, also seen in some other mammals and which may have evolved in order to promote fast and efficient communication between neurons.

Spindle neurons are thought to have first appeared in the common ancestor of hominids, humans and great apes about 15 million years ago, the researchers added. In cetaceans they would have evolved earlier, possibly as early as 30 million years ago."
So many questions. What the heck could convergent evolution produce the same neuronal structure in both cetaceans and primates? Is there only one high-probability path to [whatever] from our ancient common ancestor? What does it mean to have 30 million years of evolution working on these structures rather than a mere 15 million? How the heck did I miss the discovery of spindle neurons in toothed whales in 2000?

One prediction. If we retain a liberal civilization (vs., say, Putin's Russia), creatures with these neural structures will have "human" rights within seventy years.

PS. My guess on why I missed this? The original discoveries of spindle neurons in dolphins may have predated theories of their unique role in human cognition -- so it didn't get much media coverage.

Update 11/27/06: More memories filtering in. I think dolphins pass the "mirror test". That is, they recognize that the image in a mirror is connected with them. I believe it was recently discovered that elephants also pass this test. I think cetaceans and hippos are related, more distant to elephants. I also dimly think there's some connection between the "mirror test" and "spindle neurons". So will we find elephants have spindle neurons?

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