well some popular ideas for the evolutionary advantage of eyebrows are:
they help keep sweat and particulate matter out of the eyes, along with the structure of the brow ridge
it could also be another way to detect small insects and debris on the face, before it gets into the eye (and damage it), giving a person advance warning to remove such things from the face before they enter the eye. working as vibrissae (whiskers).
there is also the idea, of course, popularaized by British naturalist Desmond Morris, and others, that the eye brows aid so much in communication that they provide an evolutionary advantage. we are of course cooperative creatures, who rely a great deal on effective communication of intention and interpretation of mood, etc.
some people believe that when humans began sleeping on the ground, they became exposed to all sorts of nocturnal predators. many predators, like tigers, tend not to attack people face on, when they can see the eyes (but like to attack from behind or when the animal/human is sleeping.) the idea is that the line of the eyelashes and the line of the eye brow form an “eye spot” that may look like an open eye in the dark to some predators… this seems like a bit of a stretch to me, but its an idea that’s out there.
Not entirely, and no not the way you mean it, so let’s say…
No, and here’s why. There is an overwhelming body of evidence that evolution occurs, and has occurred over the duration of life on Earth. There is simply too much evidence to honestly consider the phenomenon of evolution as a “theory”, even though it IS a scientific theory. I like to say though, that evolution is a fact.
At one time there were no chimps, but there were Deinoneichus. Now, there are chimps and no animals recognizable a Deinoneichus…
We can actually watch organisms, like fruit flies, evolve over generations in much less than a human life time. The selective breeding of domestic animals over time is evolution in action (look at the various forms/breeds of pig, cow, dog, and other animals that have departed radically in form from their wild sources). There is the evidence from comparative embryology of vertebrates, modern knowledge of genetics and rates of genetic variation, the fossil record and geologic stratigraphy, knowledge of zoogeography, understanding of plate tectonics and continental drift, the ability to date both rock and organic material with an amazing amount of accuracy, comparative anatomy and physiology, and comparative biochemistry.
At this point, there is simply too much evidence AND direct observation to classify evolution as a theory in the popular sense f the word. It is fact. There simply is no reasonable conclusion one can reach scientifically, after over 200 years of work in geology, zoology, genetics, chemistry and a variety of other fields have independently lead us in this direction.
Life on Earth did not start as it is now. It started in a very simple way, probably from one kind of organism, and it branched out into the multitude of complex forms you see today… you and me and the snail and the oak tree, etc. Life continues to evolve right now. Selective pressures and horizontal gene transfer and random genetic mutation are working to change organisms as populations, slightly ever so slightly so that one day they will be markedly different organisms.
To understand all this, one does need to read a bit, but there is so much evidence, there has been so much work… there are very good reasons that the VAST MAJORITY of scientists operate under the framework of evolution, as scientists. I do not use the word “believe”, no more than i would state that I believe that there is gravity or that water will evaporate at a certain temperature under certain conditions.
If you have any more comments or questions about evolution, or the theories of how it operates, feel free to ask. Also, the work is there…