Finally, two consecutive posts that discuss the issue...
I posted something similar to johnson's view long ago. I cannot see how biological conditions will determine how a child is nutured by its parents.
As for reasons, Iunny... The middle class family ideal that holds sway today emerged during Queen Victoria's time (ie the 19th century). Before that, if I am not mistaken, 'families' existed to support the parents, not to nuture the children. So from that we can assume that the idea of a family has changed at least once, and for the better most would argue, so why can it not change once again?
(That's only one reason of many, but I could also go into details with pack relationships amongst animals, insects being left to fend for themselves at birth, etc. Maybe you should leave the argument at the human level
).
Edit: I have been visiting this thread every so often in the hope that a proper discussion would reemerge from the depths of stupidity that it had reached some time ago... Perhaps the thread could now be left to the topic at hand?