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Quirks & Quarks May 3, 2003
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Making Humans
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Darwin's Evolution? |
One of the most interesting questions science can try to answer is what makes us human. What distinguishes us from our hominid ancestors and ape relatives, and gives us the unique complement of abilities that we celebrate as our humanity? Dr. Sean Carroll, a geneticist and investigator at the Howard Hughes Medical Institute at the University of Wisconsin set out to answer that question, as best science can.
The answer is perhaps surprising. As science digs deeper into the puzzle of what makes humans unique, we find that the differences between humans and our relatives are small, and subtle. Looking at our ancestors, it's impossible to find a feature or quality that would suggest they are less capable than us. Comparing our brains to those of chimpanzees, we're finding more and more that the structures and anatomy are more similar than different. Those parts of the brain we connect with unique human abilities, like language, exist also in the chimp brain. Comparing us genetically to chimps, or even mice, we find a great similarity between our genes.
At this point we don't know a single gene possessed by humans, but not possessed by chimps. The genetic difference between us is in subtle alterations of the genes or how they're used in development. It turns out we are different in kind, not in nature. This means untangling the puzzle of our humanity will involve painstaking and detailed work to uncover the small but obviously significant differences that make us what we are.
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Papillon Polarization
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Heliconius cydno, courtesy Alison Sweeney |
Butterflies are known for their beautiful colouration, but some of the most spectacular are the iridescent butterflies. The fine textured surface of their wings reflects certain wavelengths of light, giving rise to shimmering greens, violets and blues. Alison Sweeney, a Ph.D. candidate in the department of Biology at Duke University, has shown that butterflies, who can perceive the quality of polarization in light, use the patterns we see as iridescence as an additional visual cue in jungles where the ambient light is bad. It helps them with mate recognition when colour is a less useful cue.
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Mighty Mutant Mouse
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The Mutant Mouse, courtesy Dr. Zheng Cui |
Sometimes a lab accident turns into a great discovery. That's what happened to Dr. Mark Willingham. He's a professor of pathology at the Wake Forest University School of Medicine. He and his colleagues were studying cancer in mice, and discovered one mouse that refused to get tumours. Further study showed that this mouse, and its offspring were completely cancer resistant. Now Dr. Willingham has a whole colony of cancer resistant mice, and is using them to try and understand how cancer resistance can develop.
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The Journey of Man: Our genetic odyssey.
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Fossil evidence has told us a lot about humanity's migration out of Africa. But it can't fill in all the gaps, so scientists have looked for other ways to chart our species' movement. One of these has been through the analysis of DNA. Dr. Spencer Wells was part of that drive to understand migration, and he recorded the story in his new book, The Journey of Man. From our origins in Africa, humanity moved out in two waves, one along the coast towards Australia, and another through the plains of Asia. The Journey of Man is published by Princeton University Press.
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Question of the Week: Sun Rotation
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Doug Payne from Timmins, Ontario, asks,"I've read that the sun rotates every 25 days at its equator, but slower at its poles. How can this be?"
For the answer, we shined a light on Dr. Ken Tapping, a solar astronomer at the National Research Council Observatory in Penticton, B.C.
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