Posted on 12/17/2007 1:50:35 PM PST by blam
Ape To Human: Walking Upright May Have Protected Heavy Human Babies
For safety, all nonhuman primates carry their young clinging to their fur from birth, and species survival depends on it. (Credit: iStockphoto/Graeme Purdy)
ScienceDaily (Dec. 17, 2007) — The transition from apes to humans may have been partially triggered by the need to stand on two legs, in order to safely carry heavier babies. This theory of species evolution presented by Lia Amaral from the University of São Paulo in Brazil has just been published online in Springer’s journal, Naturwissenschaften.
For safety, all nonhuman primates carry their young clinging to their fur from birth, and species survival depends on it. The carrying pattern changes as the infant grows. Newborns are carried clinging to their mother’s stomach, often with additional support. Months later, infants are carried over the adult body usually on the mother’s back, and this carrying pattern lasts for years in apes. However, this necessity to carry infants safely imposes limits on the weight of the infants.
Through a detailed mechanical analysis of how different types of apes - gibbons, orangutans and gorillas - carry their young, looking at the properties of ape hair, infant grip, adult hair density and carrying position, Amaral demonstrates a relationship between infant weight, hair friction and body angle which ensures ape infants are carried safely.
Amaral also shows how the usual pattern of primate carrying of heavy infants is incompatible with bipedalism. African apes have to persist with knuckle-walking on all fours, or ‘quadruped’ position, in order to stop their young from slipping off their backs.
The author goes on to suggest that the fall in body hair in primates could have brought on bipedality as a necessary consequence, through the strong selective pressure of safe infant carrying, as infants were no longer able to cling to their mother’s body hairs. In the author’s opinion, safe carrying of heavy infants justified the emergence of the biped form of movement. Although an adult gorilla is much heavier than an adult human, its offspring is only half the weight of a human baby.
Amaral concludes that this evolution to bipedality has important consequences for the female of the species. Indeed, it frees the arms and hands of males and juveniles, but females have their arms and hands occupied with their young. This restriction of movement placed limits on food gathering for biped females carrying their infants, and may have been at the origin of group cooperation.
Reference: Amaral LQ (2007). Mechanical analysis of infant carrying in hominoids. Naturwissenschaften (DOI 10.1007/s00114-007-0325-0).
Adapted from materials provided by Springer.
Or then there is the obvious... If you don’t have to walk on all fours, then you can use your hands for something else.
Yeah, right. Women know better.
I think that's when the saying, "Monkeying around with your privates" all began ...
Evolution is not triggered by “needs;” it is triggered by random, uncontrolled(able) gene mutations that have nothing to do with the life experience of the parent.
This is the usual LaMarckian popular science drivel.
“Evolution is not triggered by “needs;” it is triggered by random, uncontrolled(able) gene mutations that have nothing to do with the life experience of the parent.”
Yes, but the point of evolution is that, among the many gene mutations that occur, some make it more likely that the affected individual will survive to produce offspring. If, for instance, walking upright made it more likely that the offspring would be born, then that mutation would be more likely to be passed on to the next generation, regardless of whether it had any other appreciable effect on the life experience of the parent.
The “randomness” may simply be changes caused by changes in nutrition or other environmental factors that could not be predicted at the time of birth.
There are an incredible number of mutations that would have been necessary to simultaneously transform a knuckle dragger into a fully functional 2-legged walker, e.g., dramatic changes to the inner ear which regulates balance.
What good would a slight genetic change do that caused a four legged walker to slightly rear up??
This is a huge problem with this idea of 4 to 2 legged transition.
The only real advantage could be that your hands are now free, but how often do we use our hands when in motion? Most hunting and gathering can be done while sitting or standing in place
... or maybe God knew what he was doing :)
Oh yeah, science is so evil....LOL...
I saw a dinosaur the other day... he said he never existed but instead was a magical “test” by our lord.... Xinua from the planet Zorocan.
I'd call this an hypothesis.
Gotta love science!! With this new info I am armed and dangerous.
Who said science was evil? Why do you presume that creation and science are incompatible? In fact, it’s nice to see that science has come around on the question of whether the universe was enternal. Three cheers for God and his big bang!
Why do you assume "knuckle-dragger" to bipedalism is the only possible mechanism?
How about brachiator to various terrestrial adaptations, including both bipedalism and knuckle-walking?
Well, *she's* a lesbian. ;')Pregnant? Backache? Thank evolutionPregnant women may stand out a mile away with their characteristic backward-leaning stance, but that clumsy-looking position is a unique adaptation that evolved over millennia... Pregnant pre-humans appeared to have stood the same way. And it may save women from even more back pain than they already have... The bodies of women do two things when they are pregnant -- they adjust their stance to move the center of gravity to accommodate the growing fetus, and the lower vertebrae have evolved a distinct shape to allow this shifting to take place without damaging the spine... Whitcome and Shapiro followed 19 women through their pregnancy, using digital cameras and motional analysis equipment to map the changes in stance and movement as the months passed... Without this change in shape, the vertebrae could be subject to shearing forces, with one sliding over another, damaging the fluid-filled discs in between or pulling on ligaments and muscles... When she moved to Harvard, Whitcome continued the study and looked at the fossils of pre-humans known as australopithecenes, as well as at the bone structure of our nearest living relatives, the chimpanzees... Men do not have this adaptation, either, Shapiro said... "They probably lean back the same way to try and balance that load, but they are kind of putting their vertebrae more at risk. I am sure there has got to be a correlation between having a big beer gut and having back pain," Shapiro laughed.
by Maggie Fox
Health and Science Editor
Reuters
Wednesday, December 12, 2007
ed. by Will Dunham and Sandra Maler
I guess the some apes just refused to stand up in an effort to avoid putting on clothes and going to work. These are probably the apes that want to hold on to their culture. I have a neighbor that appears as though he's reverting back to an ape. He even put up a tire swing for his kids.
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