Molecule of the Month: Dads.

You may (or may not have) noticed that we have a tendency of writing about science on FTDM, but what does Father's Day have to do with science? Well, have you ever wondered how your dad became a dad? Okay...let's keep it PG. Really though - does the phrase "You won't know until you have your own." sound familiar to you?

What's up with that?
Why do human parents have an innate tendency for unconditionally loving their children? There's more science to it than one might think, my beautiful reader.

Let's step back and look at humans from an objective point of view:

Females possess a finite amount of eggs. At birth, we are born with roughly 1 million! By the time we reach puberty, however, this number drops to about 300,000. Of these, only a 1 in 1000 will make it through the ovulation stage of a woman's period.  A fertilized egg requires approximately 9 months of gestation before birth. This means that if a woman were to start having children at the first sign of menstruation and continue consecutively until menopause, she would average 55 children. That's a lot of children!

Now let's discuss the human male. At any given time, a male ejaculation contains about 100 million sperm. Why? This is because there are a lot of obstacles that can prevent male sperm from traveling to the egg in a female uterus, including the condition of the sperm itself. As we're all well aware: quantity and quality are not interchangeable. Therefore, when it comes to sperm, there is strength in numbers. Hypothetically this means that a human male can have millions of children - this is where fathers come in.

A quick clip summarizing the process of fertilization (and some of the hurdles sperm must overcome in order to form a zygote with the egg).

Based on this objective perspective and comparison of female-male interactions in other mammals, one would think that humans would favor polygyny. However, as Dr. Daniel Kruger and colleagues in his field have investigated, this is hardly the case. Humans are more inclined to be monogamous because of the investment each partner has in their children. Whatever the dynamic of the relationship (mother-father, mother-mother, father-father, and so forth), one can understand how the support of two parents can assist in children's success over one parent. 

This notion of child investment by both parents incorporates a concept that Ecologists are all too familiar with: r vs K selection. As humans, we are K selective. Here's why (those with short attention spans can skip to 4:30 for the summary):

When we think about human mating with respect to K selection, it makes sense as to why we are inclined to be monogamous, especially when it comes to dads. Investing in children is more than pure unconditional love, it's a genetic investment (sorry to crush all of the wonderfully sappy Twitter Father's Day shout outs with this one). As mentioned, quality is better than quantity. It's impossible to spend time with 100 million kids, assuring that they all reach maturity and pass along your genetic information. It's very possible, however, to spend time with 4 kids and ensure that they receive the love and care needed to become great moms and dads of their own one day, passing on your genetic information for centuries.


With all of this said and done, what's your take on human dads? Comment below, we'd love to know about it.