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?

Because we don't live for 170 years.

We live an average of around 80 - and that's only become common in the past hundred or so years (not counting, of course, exceptional individuals) so our reproductive cycle evolved in a primate that lived, on average, 30-40 years.

Jesus, women are hissy about being preggers for just 9 months . . .

So why not a weekly pregnancy?

What would the parents do with a baby smaller than a pencil eraser ??

(October 31, 2014 at 4:49 pm)vorlon13 Wrote: What would the parents do with a baby smaller than a pencil eraser ??

No, what if we evolved so that the foetus grew quickly enough so it would survive after a week?

Why 9 months?

A full term size baby in a week would drain mom totally and leave her a withered husk.

(October 31, 2014 at 4:57 pm)vorlon13 Wrote: A full term size baby in a week would drain mom totally and leave her a withered husk.

Not if she evolved not to... you're missing my point my friend...

More importantly, why are some aphids born pregnant with their granddaughters?

Quote:Some aphids have telescoping generations, that is, the parthenogenetic, viviparous female has a daughter within her, who is already parthenogenetically producing her own daughter.

http://en.wikipedia.org/wiki/Aphid

Just saying I could do with about 10,000 or so fewer aphids.

(October 31, 2014 at 4:59 pm)lifesagift Wrote:

(October 31, 2014 at 4:57 pm)vorlon13 Wrote: A full term size baby in a week would drain mom totally and leave her a withered husk.

Not if she evolved not to... you're missing my point my friend...

So, basically you're asking why human beings evolved one way and not another as regards gestation and reproduction?

Short answer (and I'm not a biologist, by any stretch): We've evolved the way we have because it works. How do I know? Because if it didn't work, we would have evolved some other way.

Your question is fatuous on the face of it. It's like asking, 'Why are trees made of wood and not cheese?' or 'Why do goats have horns and not flippers?'.

Boru