Modern human societies are obsessed with breasts.  We look at them, talk about them, enhance them, and use them to sell everything from toothpaste to luxury cars. What is our fascination with boobs? When did it start? Although many will say it is a modern thing and yet another sign of our disintegrating morals, the truth is we have had a thing for breasts for a very long time. The Process of evolution general takes a long time, so if you see a structure or adaption on a modern animal, it has roots that go way back in history. There are several different mechanisms involved in this process and today we will talk about one that Charles Darwin came up with but is not as well known as natural selection.  

Most people are familiar with natural selection or “survival of the fittest”. The idea that environment and pressure from other species will shape the adaptations that evolve in a particular species. Things like the giraffes long neck or the camouflage coloring of a toad are easy to explain by natural selection. However what explains the fact that many species develop structures that don’t help them survive, and in some cases make it more difficult to survive. Two words: sexual selection. When a structure evolves that has no survival purpose then it most likely evolved because of the opposite sex selected for it. This is not an unknown process to us, if you think about a dog breeder trying to get a particular trait like hair color, they will choose animals to mate that exhibit that color and the pups will have a better chance of also being that color. 

One of the easiest places to see sexual selection in the process is the bird world. If you look at the bright red coloring of a male cardinal or the excessively long tail of the peacock it is obvious that those adaptations are not making it easier to survive. However, if they evolved then they must serve a purpose. Back in the 1800s, Darwin was the first to point out that maybe it was the females that were driving the evolution. Other biologists at the time fought the idea and it took almost 100 years before the theory of sexual selection was taken seriously. The idea was that the reason bright colored feathers and long tails in males evolved was that the females like them. If peahens regularly selected males with a slightly longer tail them their offspring would be more likely to have longer tails as well. Over time this causes the entire species to develop long tails. At some point, the tail becomes so much of a hindrance to survival that they do not get any longer. It becomes a balance between female choice and the ability to survive.

If you look at any of our closest relatives like chimps and bonobos they have fairly flat-chests unless they are lactating at which point they fill with milk and plump up. No other ape has permanently full breasts as humans do. Humans develop plump breasts at puberty which then remains for the rest of their life. The timing of this correlates directly with when human females historically were starting to look for a mate. This suggests a connection between finding a mate and breast size. Sexual selection is a fairly complicated evolutionary process so it is not as simple as “men like boobs, boobs get bigger” however if men were selecting mates based on breast size then over time the female chest would evolve to be larger and permanently so. The question of why men are so attracted to breasts is still being debated and no clear answer is available, but the fact that they have been selecting mates based on breast size is a fact. 

We know this opens up a big can o worms about body image and the beauty culture, but remember that compared to our ape cousins an A cup is considered large. So regardless of your bra size, you can be assured that you are exactly what you have evolved to be.

This is a very brief overview of the theory of sexual selection and we encourage you to dig deeper and learn more if you are interested. We hope we have given you something to think about and remember that we all love boobs and apparently so did our ancient ancestors.  

Keep Evolving, E