The sperm race

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Every year roughly a million fertility treatment cycles are carried out in the EU and the US, and two-thirds of them fail. It takes an average of three cycles for a couple to conceive. When the treatments fail, those involved pay a heavy emotional and financial price. Sperm is produced in the hundreds of millions, which suggests that a reasonable proportion will successfully make it up the female reproductive tract. This is not the case. We know that high sperm DNA fragmentation leads to lower fertilisation rates and doubles the risk of miscarriage, so the selection of sperm with the best DNA integrity is crucial.
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The sperm race: How an Irish firm is finding the strongest swimmers

The study found that human eggs release certain chemicals to attract the right sperm and that the chosen sperms may be from an entirely different male than the one chosen by the woman to be her partner. Evolution is a brutal process which only allows the strongest and the fittest to survive. The subtle signs of this natural selection theory are seen in the complexities of human mating and sexual behaviour, where women are shown to chose specific partners that are genetically suited to producing a fit offspring with more chances of survival. Various theories exist about how a woman or a man chooses the right partner.
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The sperm race: How an Irish firm is finding the strongest swimmers

Coloured scanning electron micrograph SEM of healthy spermatozoa emerging from a cavity in the rete testis of the testes. The idea that millions of sperm are on an Olympian race to reach the egg is yet another male fantasy of human reproduction. Before science was able to shed light on human reproduction, most people thought new life arose through spontaneous generation from non-living matter.
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