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Why the hell do humans still have sex? Scientists finally have the answer

Posted April 4, 2017

Why in the world do we have sex? Seems like a stupid question, doesn‘t it? But for the scientists it is one of the fundamental mysteries they are trying to solve for ages. Science cannot say for sure why humans and most of other animals need sexual reproduction but a recent study showed disease-causing microbes might have caused us to have sex.


Sexual reproduction is actually very inefficient. Image credit: Vinicio97 |


The truth of the matter is that sexual reproduction is not very efficient. It is a difficult concept to grasp, because we grow up considering sex a normal piece of human life. However, if you would think about it from evolutionary perspective, asexual reproduction is simply safer and more efficient. For example, humans would save a lot of energy if they laid unfertilised eggs or bud off a piece of their body. That is why scientists were scratching their heads for quite some time – “Why sex evolved at all?”

There was one possible explanation, which has been dominant in this field for decades, is Hill-Robertson Interference. It states that sexual reproduction allows individuals with more than one beneficial mutation to be born. However, this explanation did not touch upon why sex survived in well-developed populations. Why we did not evolve a better way of reproducing?

If the environment is not changing and there are no external forces driving the need for genetic exchange, animals and humans would not need the sexual reproduction as such. It is only beneficial if something is changing in the living environment. Now scientists think that so-called Red Queen theory should be brought into the equation to solve the riddle. This theory argues that bacteria, viruses and parasites are continuously adapting to us and we have to continuously evolve to remain resistant to them. Needless to say, researchers are very proud of their idea to combine these two theories.

Dr Jack da Silva, senior author of the study, said: “Either on their own can’t explain sex, but looking at them together we’ve shown that the Red Queen dynamics of co-evolving pathogens produces that changing environment that makes sex advantageous through the simple genetic mechanism of the Hill-Robertson theory”. Computer simulation confirmed that combination of the two theories would actually work and does not contradict with other experiments and scientific knowledge.

So that is why we need sex – to protect our offspring from their own pathogens. Not as romantic as we made it look like.


Source: University of Adelaide

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