Menopause is a mystery and Ngogo chimpanzees make it more of a mystery!

Elderly Ngogo chimpanzee. Image: Sci News.

In terms of the evolution of animals as per Charles Darwin's theory of evolution, which is very widely accepted nowadays, the menopause of a number of primate species and of humans is somewhat of a mystery.

Perhaps you are like other men (including me) in not really thinking much about the female menopause and its purpose - some people think that the male human can also have a menopause. What I mean is why does it happen? What's the purpose of the female menopause?

It cuts short a female's ability to procreate and procreation is important in terms of the survival of the human and some primate species and their evolution. The more people there are the more chances there are of creating better people in terms of their genetics and survival.

The answer may be that after the menopause, a female becomes a grandmother and the grandmother can help raise the offspring of their daughters and sons - the 'grandchildren'. In other words, the Ngogo chimpanzee grandmother becomes a grandmother like a human grandmother and helps to raise the kids as it is very demanding.

Without the menopause there would be no 'useful grandmother' to carry out this function. This is called the "grandmother hypothesis".

My research on this also tells me that Ngogo chimpanzees live long lives of about 33 years which is about twice as long as that of other chimpanzee communities and within the 27–37-year range of life expectancy at birth of human under-gatherers.

However, the research today as published in the Times states that grandmother Ngogo chimpanzees do not get involved in raising the 'grandchildren'. In a new study, the researchers looked at 66 females and they estimated that these females spent 20% of their life unable to reproduce as like humans they have the menopause but unlike humans "they do so without lifting a finger to help with their grandchildren."

If the grandmother does not help with raising the kids as is the case with the Ngogo chimpanzees, this undermines the theory 'grandmother hypothesis' thus making the menopause a mystery to this day.

The research is published in the journal Science. And in this research, they also state that the fact that the grandmother does nothing does not totally kill off the grandmother hypothesis. It allows the grandmother to be a "doting grandmother" which may serve some use.

Another theory is that female primates of certain species have the menopause in order to make them less alluring to prevent them competing with their daughters for reproductive opportunities. We don't know at the moment.

Note: as you can see this is nothing to do with cats! I just fancied doing it as it may help some people to better understand the human female menopause.

---------

P.S. please forgive the occasional typo. These articles are written at breakneck speed using Dragon Dictate. I have to prepare them in around 20 mins.