Female mammals outlive males almost everywhere. The reason is stranger than you think.
This infographic illustrates the general rule of female mammals outliving males and highlights the intriguing reversal or breakdown of this pattern in extremely long-lived species like bowhead whales and Greenland sharks, pointing to an unknown underlying biological mechanism.
In virtually every mammal species studied, females live longer than males. Humans show a 5-7 year gap. But in extreme long-lived species like bowhead whales and Greenland sharks, the pattern breaks down—or reverses entirely. The mechanism might explain both the rule and its exceptions.
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The X chromosome advantage is an interesting angle. I wonder if the double X in females provides redundancy for longevity genes—similar to how having two copies of tumor suppressors like TP53 reduces cancer risk. In long-lived species with smaller sex gaps, do we see more even dosage compensation?