scientists discovered the reason for this phenomenon

scientists discovered the reason for this phenomenon


Menopause does not occur in the vast majority of animal species: they don’t have a period when older females just live and don’t have the ability to give birth. Instead, they continue to produce eggs until they die.

Besides chimpanzees and humans, scientists have found evidence of menopause in only five species – and all of them are cetaceans.

Scientists tried to find out why some whales (in particular, killer whales) at a certain period of evolution there was a need for menopause.

It turned out that menopause is associated with longer life spans and support of offspring by “grandmother killer whales”.

The research was published in a journal Natureand more details were told about him The New York Times.

Menopause is the period of a woman’s life when the ovaries stop producing estrogens, reproductive function fades, and fertility ceases.

However, this phenomenon is quite rare among animals. Even long-lived animals usually follow this pattern: for example, female elephants remain fertile up to 60 years.

But 5 types of whales do not “fit” into this scheme. For example, female killer whales usually only breed until they are 40 years old, but can live up to 90 years.

Therefore, a recent study focused on five species of cetaceans that experience menopause (orcas, false killer whales, belugas, pilot whales, and narwhals).

Biologist Samuel Ellis from the University of Exeter believes that menopause could have appeared in whales for the same reasons as in humans.

Orcas are relatively easy to study because they often swim in coastal waters, while other species spend more time diving far from shore. So instead of chasing the whales, scientists analyzed information from data that marine biologists had already collected.

Sometimes groups of whales wash ashore en masse. When marine biologists examine the bodies of animals, they estimate their age and perform autopsies on females to determine whether they are pregnant or fertile.

Dr. Ellis and his colleagues collected data on five cetacean species that go through menopause, as well as 27 related species that do not go through menopause (such as dolphins and sperm whales).

Using statistical equations, Dr. Ellis and his colleagues estimated the whales’ average lifespan, number of offspring, and length of fertile period.

In species that do not go through menopause, there is one trend: larger females tend to live longer. However, among the five species that have menopause, a different phenomenon is observed.

Female whales remained fertile for as long as is possible for whales of their size, and then lived an average of 40 years longer than their predicted lifespan.

Scientists have concluded that the evolutionary cause of menopause in killer whales may be genetic changes that allowed the animals to live longer even after the cessation of reproduction.

The development of this reproductive behavior gives killer whales several bonuses. First, old females do not become pregnant at the same time as their daughters. Therefore, they do not compete for resources with their own offspring.

Researchers suggest that this is what, in the long run, allows the whales to pass on more of their genes and preserve as many offspring as possible.

In addition, older females can provide assistance to younger ones, as long as they do not compete with them. In previous studies, scientists have found that older killer whales become guides for their pods when traveling.

And “grandmothers” can get additional food, which increases the chances of survival of their “grandchildren”.

It seems that this species needs such an arrangement, in which females live in a group for a long time and communicate closely with young killer whales, he adds Samuel Ellis.


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