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Environment major factor in growth.

If you volunteer to colonize the moon or Mars, you can expect your kids born there to look different and move quite differently than you do by the time they start kindergarten. Then, if you plan to send them to boarding school on Earth, you may need some extra cash for a wheelchair, golf cart, or caretaker to help them move about, maintains Dennis Carter, a Stanford University specialist in biomechanical engineering.

Current scientific explanations of how we become who we are may overestimate the role of the genome inside that single cell from which all humans begin. Carter contends that it will not take generations of genetic evolution in a changed environment to substantially change your descendants. He and his students have demonstrated that bones aren't told how to grow by the genome nearly so much as they are shaped by biomechanical construction rules, which are based on the environment inside the womb and on Earth. Just as there are rules for constructing bridges and buildings that will stand up to the physical forces in their environment, so there are rules for the construction of bones--and, most likely, other tissues--within an animal species.

Carter and his class have been able to write those rules, in the form of mathematical formulas called algorithms, for bones in a variety of species, living and extinct. The rules can be expected to drift over millions of years through genetic selection or evolution. Run in a computer program, they can help predict the effects of different environments on bone development. "These algorithms are a brilliant mechanism for survival, and they could evolve differently for each gravity field," Carter maintains. The bones of all Earthlings would adapt on Mars, but by far the most change would occur in those conceived and born there.

Human skeletal construction begins in the womb, where the local cellular environment pushes and pulls developing cartilage that eventually will ossify into bone. Researchers have found that bone orients itself towards principal stresses and becomes most dense where those stresses are greatest in order to resist them. The hip joint, for instance, is a ball and socket upon which the pelvis puts tremendous tensile and compressive stresses, in turn determining where the bone is dense and where it is porous.
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Title Annotation:bone growth
Publication:USA Today (Magazine)
Date:Oct 1, 1993
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