Question #5: Is Human Evolution Accelerating
"...saying that it remains difficult to ascertain whether or not certain genes really have recently grown in prominence because they offer some adaptive benefit."What I find interesting in this statement is the point that genes have to provide some adaptive benefit. While this would certainly be true in a normal population, it would seem fairly clear that with 6.7 billion humans on the planet that our survival isn't particularly stressed, at least not from a biological perspective. Certainly there are many factors that affect survival, but the overwhelming majority relate far more to human politics and economics than they do to biology.
It would seem that with such a large population base, the opportunity for many genes to exist without explicitly conveying a benefit is not only possible, but quite likely. In effect, we would expect to see numerous variations in existence provided they are not explicitly harmful, although even in the latter case, modern technology may still ensure fitness is preserved.
"Still, if human evolution is accelerating, the question becomes why?"It seems clear that if natural selection doesn't eliminate or reduce fitness of individuals, then the alternative is that all genes being spread through a population have an equal likelihood of spreading. As a result, the more individuals survive, the greater the acceleration of "evolution".
Question #1: Why Did We Grow Large Brains?
This question along with the previous one "Why Do Humans Walk On Two Legs", strike me as being asked backwards. In other words, the question itself implies a direction to natural selection that simply doesn't exist.
"So what kicked off the push for a larger brain? One possibility is that increased smarts helped our ancestors make better tools. Another is that larger brains helped us interact better with each other. Perhaps radical changes in the environment also demanded that our ancestors deal with a shifting world."As can be seen, the statement implies that somehow our ancestors experienced some problem and consequently evolution solved it by providing us with larger brains. This is simply wrong.
As with any adaptation or mutation, the organism simply has to contend with what it has. If a particular variation conveys an advantage such that overall fitness is increased, then there is a greater likelihood that such a change will propagate into future generations. It could just as readily have been three arms, or two brains, or any number of things that might be advantageous or detrimental. In hindsight, it always looks purposeful, but the question, as asked, is meaningless.