SCIENTISTS have worked out why female killer whales and humans have a huge milestone in common.
Both go through the menopause – a largely unexplained trait of evolution.
The only other species to stop being fertile as they get older is the pilot-finned whale.
This has long puzzled scientists, as female killer whales have a long lifespan after giving birth to their last calf, and could raise more calves.
It was initially suggested that they went through The Change so they could focus on raising their extended families – a hypothesis dubbed the "Granny effect".
But a recent study suggests a darker reason, which could be true of humans too.
Darren Croft of Exeter University's team have found that older females hit menopause when their eldest daughters become fertile.
The study – which looked at 43 years of killer whale data – found that when mums and daughters breed at the same time, the mum's calves are more likely to die.
Killer whales begin breeding around the age of 15 and then stop between the ages of 30 and 40 – despite living past 80.
But older female Orcas play an important role in the family structure too, Croft added.
“They appear to be particularly good at pinpointing places to hunt salmon, the main source of food for the resident killer whales."
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It stated: "Intergenerational conflict combined with the known benefits conveyed to kin by post-reproductive females can explain why killer whales have evolved the longest post-reproductive lifespan of all non-human animals.
Author Mike Cant added: “Our theoretical predictions have turned out to be correct.
"We have captured a key piece of the puzzle of postreproductive life. Now we can explain not just why older females live so long after reproduction, but why they stop breeding in the first place."
Last week SeaWorld finally scrapped its pool performances with killer whales after years of outrage and recent death of Blackfish star Tilikum.
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