From Ask Men. Com

2- Men have their own biological clock By Ross Bonander
Entertainment Correspondent - Every Wednesday PAGES: 1 | 2 |
We do indeed have a biological clock of sorts, although instead of one that stops, ours becomes increasingly unreliable over time.

As men age they lose approximately 1% of testosterone every year. The consequence of this deficit is that sperm production decreases, and those that are produced are of a lower quality. For this reason, the older we get the greater the chances that the children we spawn suffer from conditions such as autism, schizophrenia and Down syndrome, to name a few.

To explain why, fertility experts point to cell division: About every 16 days the cells that create sperm and determine their genetic code go through the process of dividing. By the age of 50 that division has happened hundreds and hundreds of times, and each time it did the genetic code was vulnerable to changes that can augment genetic deterioration, making birth defects increasingly likely.