What’s the secret to becoming a good father? What would William Cosby do?

I for one have no idea BUT! a study published today in PNAS early edition finds an association between studly vs. paternal behavior, and levels of everyone’s favorite hormone, testosterone (T).

Using longitudinal data, researchers (Gettler et al. in press) found that, in general, a young guy with higher levels of circulating T is more likely than a guy with low T to become a father w/in a few years. MOREOVER! this erstwhile-high-T-and-now-father then experiences a relatively sharper decrease in T than would be expected simply because of aging. PLUS! fathers who interacted with their kids on a daily basis had lower T than fathers who didn’t hang around their kids too often.

One thing neat about this study is that it uses longitudinal instead of cross-sectional data.  A cross-sectional version of this study would’ve sampled a bunch of dudes (hopefully somewhat randomly) only once. This can be problematic because it’s then hard to interpret the results in light of the many sources of variation between people. This study, on the other hand, sampled a tonne (n = 694) of guys at more than one occasion, so they can tell how individuals’ testosterone levels tend to change in paternal vs. free-spirited circumstances.

The last line of the paper is pretty intriguing: “[these results] add to the evidence that human males have an evolved neuroendocrine architecture shaped to facilitate their role as fathers and caregivers as a key component of reproductive success.” (Gettler et al. in press: p. 5/6) This is especially interesting in light of the Ardipithecus ramidus-related evidence for a great antiquity of humans’ paternal proclivity (Lovejoy 1981, Lovejoy et al. 2009). Just how and why testosterone responds to/mediates this fatherly ‘reproductive strategy’ is mysterious to me. And of course, linking this hormonal phenomenon with anything as old as Ardi is a challenge I’m certainly not up to. Still neat, though.

My personal circulating T levels are consistently through the roof. So in the event that I become a father, it will be interesting to see if the subsequent, astronomical hormone drop, predicted by this study, won’t cause my entire body to collapse in on itself.

Reference
Gettler LT et al. in press. Longitudinal evidence that fatherhood decreases testosterone in human males. Proceedings of the National Academy of Sciences… doi: 10.1073/pnas.1105403108

Lovejoy, C. (1981). The Origin of Man Science, 211 (4480), 341-350 DOI: 10.1126/science.211.4480.341

Lovejoy CO (2009). Reexamining human origins in light of Ardipithecus ramidus. Science (New York, N.Y.), 326 (5949), 740-8 PMID: 19810200

Photo credit: google (image) “Bill Cosby Fatherhood”