by Roger Bourke White Jr., copyright April 2023, July 2025
Evolution is intensely practical, and here are some examples.
Evolution mystery: the benefit of yawning
Is there a DNA competitor?
Why male herbivores have big elaborate horns
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?
Humans, dogs and cats yawn. It seems that horses, cows and sheep don't. Why the difference? It seems that yawning is a reflex that carnivore mammals engage in but herbivore mammals don't bother to do. Since evolution produces very practical results, this implies that yawning is a benefit to carnivore thinking but not of value to herbivore thinking. If so, what is the benefit? Currently, it's a mystery to me.
DNA is a chemical-based memory system that can not only save information and pass it on, it can also be modified so that the information can be expanded, improved and reproduced. Wow! What a combination! This is at the heart of evolution as we experience it here on Earth.
That brings a question to mind: Are there other chemical systems that can do comparable activities? Another way to put this is: Is there a way to do life without DNA and the chemical systems that surround it?
If there is, this certainly expands the conditions that can support life. If there isn't, then Earth's surface can be considered an even more exceptional place.
Why do male herbivores like elk, deer and moose have such big and elaborate horns? The short answer is they are a way of signaling who the females in the area should mate with.
The elaborate designs of the male horns indicate that combat is not their main function -- how they look is more important than how they function in combat. Likewise, the fact that they are on the males only part of the year indicates that combat is not their main function. (they fall off and grow back annually)
So... who cares in an important way, and when? The answer is the females when they are in heat. They use looking at those horns as part of their deciding whether to mate with a particular male, or not. This is why their elaborate shape is so important -- it is appearance that counts the most.
What the benefit to the species is for having females admire males with big elaborate horns remains a mystery to me.
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--