Evolutionary mechanism: Golgi tendon reflex

Popular-level books and news stories in areas like evolutionary psychology can sometimes leave the reader with a mistaken impression that all humans are "evolved for" X, where X is the specific environment in which our species arose.

I’m not an expert, but here’s one of the things I understand to be wrong with that picture: because every organism experiences a slightly different environment, and every environment is constantly changing to some degree, it is far more advantageous to have a basic set of "modules" that can be applied to a wide array of situations, rather than simple "rules" of "X is good, Y is bad".

For example, consider pain. Chordates (like us) could have evolved such that pricks and pinches simply caused us to immediate retreat, without any of the complications of experiencing nociception (http://en.wikipedia.org/wiki/Nociception). Or consider sleep; we could have developed such that our sleeping patterns were involuntarily tied to the time of day or level of sunlight, a simple "light switch" system. One reason that those things are not that simple is the fluctuating nature of the environment. After all, it’s not always the case that pain-causing things should be avoided, just usually so. (There can be situations in which it is necessary to bear pain to escape death, or to save a fellow creature’s life). So pain acts as a persuasive "message" to guide us on the question of whether or not to withstand a bad stimulus — the more detrimental the stimulus, the worse the pain, until we reach the point of involuntary retreat from that hot stove. Likewise with sleep — our bodies "send us the message" that we need to sleep, with increasing strength as the hours pass, but it doesn’t force us to until the situation is dire.

Evolution doesn’t just cause adaptation to environments, but the adaptation to adapt — for example, the ability of some animals to change their coats in response to environment. Humans (of certain tones) can "change" our skin with the practice of tanning. By extension from this principle, human muscles can survive a fair amount of use, as well as a fair amount of disuse. You can be a body-builder or you can rest on the couch, and only at the extremes of those lifestyles are problems caused. In the reasonable medium between extremes, you simply develop whichever muscles you "practice" with. This allows for the flexibility of adapting to different environments — some environments call for stronger calf muscles, others for stronger biceps, etc. (Of course, I am also not an expert in the area of fitness, so I could just be spouting nonsense there. But I think I have the basic idea right.) Repetition is not, in itself, an issue.

The question about eyes and car speed seems similar to me. There’s no particular reason for people to evolve to not tolerate moderately high speeds, so… we can! (Although the phenomenon of car sickness is a counterpoint to that — plus, when you hit those brakes at high speeds, you probably do experience a sense of "something’s wrong"!) Driving is just one of those things we can do comfortably "despite" its extreme historical recentness, like listening to rock music, or wearing blue jeans, or staring at screens (although that last one can be problematic, for reasons indirectly tied to evolution). There still are environments too extreme for humans to survive in without special assistance and months/years of practice, of course, such as space travel. But cars/roller coasters/etc don’t reach that extreme. (Unless, perhaps, you’re going 500 mph with direct exposure to the air; but I could be wrong.)

In addition to all that, there is evidence that our evolution has itself been influenced by human activity; the brain indicates some adaptation specifically for the ability to speak and think linguistically, while our digestion (it has been argued) has adapted itself to the world of cooked food! Perhaps our distant descendants will carry instincts that specifically aid the act of safe driving… but I don’t see that as likely for a number of reasons. (One is that the selection pressure for humans is much lower in the era of modern medicine, and another is that transportation technology is going to change plenty over long periods of time.)

I just read the Wikipedia article on the Golgi tendon reflex, mentioned in the reply above, and it looks like a very good example of one of those "overriding instinct" things I was talking about. (Maybe.) Just like a certain level of pain will cause you to move whether you want to or not, this reflex deals with the problem of too much weight.

Throughout our evolutionary history, humans have had to deal with a fair amount of weight-carrying, whether it’s carrying babies (they’re heavy!) to carrying a killed game animal. So we don’t have or need some kind of "never repeatedly carry things" reflex, just this Golgi thing.

Lifting weights for a purely esthetic reason is a very recent concept in our evolution.

Each race has a different evolution that has shaped their body shape. The first thought that came to my mind was the sumo wrestlers, and how they are actually breed to be so big, in their cultural evolution. Russians, Swedes, Danes, and Finnish are all big from being in the harsh frozen environment, and their cultural evolution that came from that. I can think of different reasons why they would lift heavy weights at certain times during the day (to represent the 6-8 rep set of today’s heavy lifting) – for example the blacksmith, the ship builders, the farmers, the sailors, etc. There bodies adapted more of the heavy load building muscle fibers, than the lighter more endurance aerobic muscle fibers (which would be found on the people that had to perhaps run alot to stay alive – such as nomads that had to travel far). These traits were handed down thru the centuries, and it is only when interracial mingling of the DNA genomes, and today’s culture has diversified the body types. When lifting weights, you should try and see what works with your body type, not come up with a general rule for everyone. And sometimes you will find that the lifting heavy 6-8 rep set is not for every body part also. I know of bodybuilders who have found out that they need to lift medium 12-15 rep set for shoulders to build, and/or for their legs. This is where the mingling of DNA has produced different muscle fibers for different body parts (like for me, I do not have to build my legs as just running makes them look like tree trunks, while my delts need to be fatigued to grow just centimeters).

Bodybuilders can be very stubborn in their training though. They can actually override the golgi tendon reflex and that is where the pec tears come into play. Physically stong body can also have a physically strong mind set (not always right in the thinking though, and that is where they get into trouble. need to listen to your body sometimes, and not always just tell it what you want it to do).

Yep. Creatures aren’t boxes of "limited" abilities, where it can do X and nothing more. A dog with the ability to chase and catch a squirrel (directly benefiting it) also has the ability to chase and catch a frisbee (indirectly benefiting it).

I remember once riding in a car with my big old (late) Doberman, who had his head sticking out the window and panting — he loved car rides. My dad, "speaking for" the dog, suddenly said, "Hey, wow, look how fast I’m running!"

That illustrates one way in which organisms can be "tricked" — the dog’s brain "rewards" it for running/exercising, but the same reward partially happens also when the dog is going really fast by other means. Likewise, it can be exciting for humans to drive really fast, because it partially simulates the beneficial activity of running. (Now that I think about it, it’s actually kind of like how pornography "tricks" the human libido…)

When it comes to an ability’s neutralness… that’s actually a lot rarer than you might think. What I mean is that for every ability, there has to be some kind of tradeoff. In order to see things, you need a lot of energy constantly devoted to the eyes and brain, and your eyes themselves are susceptible to parasites and contaminants, so you need to spend additional energy on things like growing eyelashes and reflexively blinking. That’s why a species’ vision is only ever as good as it "needs" to be for its niche — we can’t see as well as hawks, but we see much better than bats. And it’s why if a group of, for example, fish spends all its time in caves, over the course of looong periods of time, it will lose vision, and eventually, its eyes. Caecilians ( http://en.wikipedia.org/wiki/Caecilian ) are a great, somewhat creepy example of a creature with very-vestigial eyes (they can tell if there’s light or not, but that’s it).