Wouldn’t we be better off with two of everything?
In: 5
We’d be better of with 4 of everything, or 10 or 100 or 1,000 if the idea is that more is better. But more comes at a cost – resources are required to create organs and keep them functioning and healthy. Evolutionarily speaking, we have the “right” balance of number, size and type of organs that fosters reproductive success generally, at least when compared to a different number, size and type of organs when viewed from the perspective of human and pre-human development over the past several million years.
Bilateral symmetry appears throughout the animal kingdom in many places, and for certain things it’s easy to see why – two ears confer the ability to hear where a sound is coming from, and two eyes (at least when placed close together) allow us to determine distances quicker. Regarding internal organs, most are solo – one brain, one heart, one liver, one set of intestines and stomach (for us – some animals have multiple stomachs that help them digest what they eat more efficiently). Lungs and kidneys come in pairs, and those might just be flukes of evolutionary history – growing two of each of these organs just worked better so that trait was passed on more and more, while growing two livers or hearts or brains might have consumed too many resources or caused other problems leading to less reproductive success and those genes dying out.
In short, the number of each organ humans tend to have is owed to eons of evolutionary pressure coupled with random “mistakes” that test whether another approach is better time and time again. There’s no plan or reasoning behind it – if a certain trait worked well, it stuck, and if it didn’t work, it was quickly winnowed out of the gene pool. Maybe in a few million years we’ll have more or less of some organ or other (or some entirely new organs), or maybe we’ll bio-engineer some other body type before then, but we have what we have because it worked to get us to this point as a species.
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