RE: Reproductive cycles
November 1, 2014 at 11:21 am
(This post was last modified: November 1, 2014 at 11:48 am by Anomalocaris.)
(October 30, 2014 at 7:13 pm)lifesagift Wrote: Why are our reproductive cycles so short?
Given that the solar system is 4.6 billion years old... why do we produce offspring in just 0.75 of a year? and not 170 years?
Why is a day 24 hours and 3546.13 years?
The gestation period is a compromise between several competing demands: Survival of the mother, survival of the fetus and survival of the infant. They each conflict with the others. The survival of the mother demands the shortest gestation period, the smallest demand upon metabolism, and the smallest fetus at moment of birth. The survival of the fetus demands substantial metabolic contribution from the mother, and the survival of the infant demand considerable size and level of development at birth without killing the mother-ie lengthy gestation. 8-9 month was apparently the best compromise between survival of the mother and survival of the fetus and infant in common ancestor of the great apes. Great apes all share roughly the same gestation period of 8-9 months
The reason why human gestation is 9 and half months is simply that during the 6 million years or so since human ancestors branched off of other great apes, there had not been sufficient selection pressure, or not enough time for the pressure to act, to change our gestation period substantially from our common ancestors with the apes.
