MartinV
I think it is not only untestable, but utterly dubious neodarwinian explanation.
The problem cannot be solved by "cooling sperma" explanation, because:
1. Some mammalian species have testicles inside their bodies and obviously haven't "cooling spermatozoa" problems.
t
2. Birds often have temperatures of 42o Celsius and do not have "cooling spermatozoa" problems either:
From this site
http://www.ossh.com/birds/budgies/gensystm.html
we get this explanation.
In common with their reptilian ancestors, the body temperature of birds fluctuates; it is believed that when it falls at night, sperm production can then proceed.
From another site
Picture Gallery - Infertile Felines | Fooling With Nature | FRONTLINE | PBS
we get this interesting bit of information.
Florida's panthers are in serious trouble. And some scientists see unsettling parallels between these large cats and other mammals, including humans. Already an endangered species, Florida's panthers are plagued by low sperm counts, abnormal sperm, undescended testicles, thyroid problems, depressed immune function, and congenital heart defects. Only 30 to 50 of the large cats survive. Until recently, inbreeding was blamed for their fertility problems. But many scientists think that manmade chemicals, like pesticides, are the real culprits.
The panthers' reproductive problems are the most severe of any cat species studied. Panthers have the lowest sperm counts, the lowest semen volume, and the highest number of abnormal sperm on record. In fact, over 90% of their sperm are abnormal. Most of the males also suffer from "cryptorchidism", meaning that one or both testes remain lodged in the abdomen. These undescended testes can contribute to sperm defects. They produce less sperm, and more defective sperm, than testes that descend properly into the scrotum. As a result of the defects, several of Florida's panthers are completely sterile and are unable to impregnate a female.
These fertility problems are eerily similar to reports of undescended testicles and plummeting sperm counts in humans. By some estimates, although the science is controversial, human sperm counts have dropped 50% over the last fifty years. What's more, a study in England showed an approximate doubling in the rate of undescended testes in three-month old boys between the 1950's and 1980's. Similar increases in cryptorchidism have been reported in Scotland and Denmark, although not in the U.S.
Since evolution does not require that our hypothesis be correct and only that the observed phenomena {undescended testicles} have no deleterious effects on the reproduction capabilities of the species.
It may be dangerous but I do not think that there is much in the way of evidence that danger has ever slowed down the human capacity for sexual fitness.
Edited by sidelined, : No reason given.
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