I studied the head and neck with a Romanian anatomist. He had a delightful accent when he spoke English–think Andrei Codrescu. We spent a lot of time talking about the skull. There’s a lot to say about the skull–the 22 bones that make it up, the multitude of foramina through which blood vessels and nerves enter and exit it, the evolution of the middle ear from the characteristic multi-part jaw bones that you can still see in lizards, I believe. Regarding the forehead, though, about all that he talked about was a structure called the glabella–the little depression between the eyebrows and above the nose. The only known function of the glabella, he said, is to insert a stake to kill a vampire. Imagine that being intoned with a strong Romanian accent and you have a fine example of the humor that characterizes the typical anatomist.
One unpleasant characteristic of scientists: we can suck the joy out of pretty much anything. On the plus side, we can find something interesting to think about pretty much anywhere. Arguably, one of the least interesting aspects of the human face is the forehead. It’s easy to find poems that go into ecstatic descriptions of the eyes and the mouths of a loved one, but I don’t recall ever reading a poem that praised someone’s forehead. There’s a lot to say about the forehead, though.
If you look at skulls of non-human great apes and of various extinct non-Homo sapiens species, one of the most distinct differences is that modern humans have a forehead, while the aforementioned others don’t, or at least don’t have the typical modern human tall, vertical forehead. Here is a nice schematic illustrating the trend in changes to the forehead over the course of human evolution (scroll down past it):
It’s also useful to look at the forehead across the range of great apes. Here is a nice picture showing frontal views of the skulls of a variety of apes, great and otherwise (scroll down past it when you’re done):
The development of the skull over the course of growth from infancy to adulthood is especially interesting, as it’s a good illustration of the concept of neoteny. Take a look again at this picture that we saw in a recent discussion of the human chin:
The top shows the development of the skull of a chimpanzee, from infancy to adulthood. The bottom shows the development of the skull of a modern human, from infancy to adulthood. The thing to notice here is that the chimp starts out with a forehead, but it goes away over the course of development. The human starts with a forehead, too, but it doesn’t go away. This is an example of a phenomenon that is often observed in the course of evolution: new species may evolve through the retention of some characteristics of the infant. This is known as neoteny. So, a dog is in some ways like an immature wolf, a domestic cat is in some ways like an immature wild cat, and so on.
The changes in the forehead over the course of human evolution are associated with a larger brain size, but interpret this fact with caution. A larger brain size doesn’t necessarily mean more intelligence–a whale has a heck of a lot bigger brain than you do. I’m not aware of any evidence that a whale is in any sense smarter than you, though, with the possible exception of the fact that humans sometimes get forehead tattoos, while as far as I know, whales don’t:
So: get out there and suck the joy out of something, but I recommend that you not get a forehead tatoo…
Zipf's Law 
I come from a family with large foreheads on the paternal side.
These proportions are also characteristic of the infant human.
My children have this characteristic;what do you think we might be developing into ?
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I ran into a couple articles relevant to your question in the course of writing this post. They seem like mostly bullshittery, but here are a couple answers:
http://www.forbes.com/sites/parmyolson/2013/06/07/how-the-human-face-might-look-in-100000-years/#6d84501d7687
http://www.dailymail.co.uk/news/article-2337804/Huge-foreheads-flat-faces-saucer-like-eyes-How-human-face-look-100-000-years.html
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No Z, you were supposed to respond by saying that you were sure it’s nothing to worry about and just explains why I am madder than a box of frogs; in a good way…
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Hey, it’s nothing to worry about. It just explains why you are madder than a box of frogs (in a good way).
I love it when people tell me what I should say, and I often do the same myself! 🙂
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This interesting post gives me a lot to think, on a phylogenetic point of view . There is obviously something to enlighten in and from this neoteny .
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It seems to be a pretty common phenomenon, evolutionarily speaking.
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Yes, but the fact a species – and as it happens mine- could develop so many extraordinary qualities maybe due to some sort of braking on certain factors and not, as we would be inclined to think a priori, due to only an acceleration of other factors opens for me a partially unexpected path . But I’m a scientific metaphysician above all .
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