by Roger Bourke White Jr., copyright April 2023
Evolution is intensely practical, and here are some examples.
Why we like drinking cold water
Men's voices being deeper
Women having monthly periods
Mammals having big tails
Why do we have male and female?
How much physical variety can a species support?
Why do we like drinking cold water rather than room temperature water?
We like it because when we are living in primitive conditions spring water is cold water and spring water is a lot cleaner and less hazardous than pond water. Pond water has been lying outdoors for a while and has had the opportunity to grow hazardous microbes. Spring water has been underground so it is more likely to be sterile and thus less hazardous to our health. Net result: we can splash and play just fine in pond water, but it is more healthy to drink spring water, and that is cooler water than pond water. That's why today we like drinking cold water.
Men's voices are deeper because the lower frequencies travel better over long distances. If you're in a hunting party, being able to communicate further is an advantage.
Women have monthly periods -- rather than annual or semi-annual ones -- to keep men close. This encourages the men to help in family raising. In most mammals child raising is mostly a mother's activity. If the females form a group then it becomes a mother's group activity -- other than in humans, males are rarely involved.
The tails are used for signaling emotions. They let surrounding mammals, particularly those of the same species, know what the mammal is thinking about his or her current situation. Are they happy or upset with their current situation? Think of a dog wagging its tail. Note that humans and gorillas do not have tails. Humans don't because they use vocal language in place of tails. This implies that gorillas also have a vocal language that can express a lot.
This one is still a mystery for me. Why not keep it simple and have both eggs and sperm in one creature? With this monosex variant mating moves sperm in both directions and both creatures have eggs that can be fertilized. What is the benefit of splitting the egg and sperm into two distinct organisms? I have no answer for this one yet. But, given how ubiquitous this arrangement is, the benefit must be a big one.
A species is a group of organisms that can mate with each other. Most species are pretty uniform in their design -- cows and humans are good examples. What is an example of the other extreme, a species with a lot of variety in it's members? One that comes to mind is dogs. Take a look at how varied dogs are in their size and structures. Yet, even with all this variation they can all still mate with each other. This is a good example of a species with lots of internal variety.
--The End--