Testosterone May Drop When Men Become Dads Sept. 12, 2011 -- Testosterone levels drop when men become fathers, and they are lowest for the most devoted dads, new research shows.

While earlier studies had also shown that fathers have lower testosterone levels than men of the same age without children, it has not been clear if men with low testosterone are more likely to become fathers or if fatherhood actually suppresses levels of the male sex hormone.

The new research suggests that the latter is the case.

Researchers say the findings show that unlike most other mammals, human males are biologically hardwired for parenthood.

"The classic idea is that men were the hunters and providers and the females evolved to raise the children," Northwestern University anthropologist and study co-author Christopher W. Kuzawa, PhD, tells WebMD. "I think our study shows pretty clearly that men are also wired for their role as fathers."

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