A recent study carried out by a group from Northwestern University has revealed that testosterone levels in men decrease greatly upon fatherhood, with the largest difference observed in fathers who are especially hands-on with raising their children. Scientists speculate that this drop in testosterone level might biologically emphasize a man’s commitment to his family, strengthen his focus on caring for his children, as well as increase his sensitivity to their needs.
The researchers collected saliva samples from 465 21-year old, single, men. This process was repeated in the same group when they turned 26 years old. Each man gave two samples, one in the morning where testosterone levels are typically the highest, and another in the evening where the levels are known to decline.
As expected, within the five year period, some men remained single, others got married but did not have children, while the rest found themselves married and settled down with kids. The single men had twice the amount of testosterone compared to the fathers in the group, while the men who were married without children had testosterone levels that fell in the middle of the two.
Going one step further, the fathers were questioned regarding their involvement in the raising of their children - whether they played with them, took them on walks, fed or bathed them. The fathers who spent more than three hours a day carrying out these activities displayed the lowest testosterone levels in the group.
Looking at this research from an evolutionary point-of-view, it indicates a possible biological response to fatherhood. The results provide a contradiction to the long held belief that the male species are hunter-gatherers while the women stayed home with the children. This decline in testosterone has also been observed in males of certain bird species that help out in taking care of the offspring.
Principle researcher Lee Gettler, a biological anthropologist, believes that this decrease could be due to the fact that women needed more help taking care of their children over the years, “Humans wouldn’t have been as successful if fathers weren’t helping. It is an ongoing debate in anthropology. But this is suggestive that caring for children is a role fathers were playing in human evolution to the extent that it has become embedded in human male physiology.”
When taking in the diversity of the animal kingdom, one cannot help but feel that Humans stick out. Going beyond the obvious fact that we are the dominant creatures on this planet (at least when pertaining to our own criteria and knowledge), evolution has also pushed us in a manner that has resulted in the loss of resemblance to our most closely related animal relatives. Perhaps it is time to get down to basics and find out what sets us apart.
Just because we have not deciphered what a dog is trying to put across when barking, does not mean that other animals are not capable of what we would consider, an in-depth conversation. What scientists have discovered, is the fact that our larynx has descended lower into our throats some 350,000 years ago, one of our distinctions from chimpanzees. This descended larynx and a descended hyoid bone, a horseshoe-shaped bone located below the tongue and not connected to any other bones in the body, are what allows us to articulate the intricacies and dynamics of human speech.
Humans remain the only animal thus far to walk upright throughout their lives. This ability is speculated to have been vital to our dominance on this planet, as it has freed up our hands for the manipulation of tools. The development of walking upright came with it’s drawbacks. The evolutionary changes in our pelvic structure, to support movement on two legs, increases the dangers of childbirth. It is believed to be one of the main reasons why childbirth was a leading cause of death in women a century ago. The lumbar curve in our lower back helps to maintain our balance as we stand or walk, but the presence of this actually increases our vulnerability to back pains or strains.
At first glance, the obvious difference between humans and our ape relatives are the lack of hairs on our bodies. Scientists have discovered that we actually possess an equal number of hair-producing follicles on an average square inch of human skin, as our primate cousins. Our less shaggy outlook has to do with humans producing much shorter, thinner and lighter hair.
Opposable thumbs? A myth
The next time someone tells you that humans are the select group with opposable thumbs, tell them that though we do possess them, apparently so do most other primates. In fact, most of the great apes have opposable big toes on their feet, not something we can boast to match. What we can do however, is to bring the thumb across the hand to meet our ring and little finger. Conversely, the ring and little finger can also be flexed to toward the base of our thumb. These two seemingly inconsequential movements are actually what gifts us a powerful grip and enables high dexterity when holding and using tools.
Most animals leave their mothers a few years after birth, but human children stay with their parents for a much longer period of time. This behavior contradicts with evolutionary principles of releasing the young so more offspring can be created. Scientists predicts that it might have something do with the human brain requiring more time to learn and mature.