It’s Father’s Day today, in the UK at least. My children, who both delight and infuriate in equal measure, spoiled me with some thoughtful presents.

This article touches on something I’ve observed in others and myself: becoming a father really does change men. As the diagram below shows, that happens in terms of testosterone, but in my experience being a dad changes your worldview.

Diagram showing testosterone levels reducing as children are born

New fathers show reduced testosterone, which may help them be more nurturing to their newborn children. Scientists sampled testosterone levels of more than 450 men in the Philippines in 2005 and again in 2009. All the men showed a slight decrease in testosterone levels (morning testosterone levels shown here), which is to be expected as they age. Men with newborn infants showed a much greater drop, however. Their testosterone returned to expected levels as their children grew up.
Source: Evolution of the dad | Knowable