Sunday 17 March 2024

Menopause in females, female mammals larger than males, & non-antibiotics | Last Week in Science (17th March 2024)

Are longer lives to blame for menopause?

Menopause is the loss of the ability to produce children by the human female. We do not know the reason for the evolution of menopause but there is a grandmother hypothesis. It says that because of menopause grandmothers are invested in their grandkids so as to ensure that their genes get passed on beyond their children's generation. The second reason might be the elimination of competition of resources between their own children and grandchildren because both the grandmother and mother won't be reproductively active or in the child bearing phase at the same time. While there is no study done in females that can explain or substantiate the grandmother hypothesis, scientists have studied toothed whales to find an answer.

Menopause is not a unique feature of humans, but other mammals like some toothed whales are also known to undergo menopause. But not all the species of whales undergo menopause. Scientists compared these different species - the ones with menopause vs the others without by looking at their lifespan and fertility. They found that toothed whales that experience menopause have longer lives than the ones who do not. But since it is not possible to go in the wild and check for how long a whale lives or can produce children, so the scientists had relied on whales that were caught by shipping vessels, whales stranded on beaches. They looked at the ovaries of these females to guess for how long the whales would have been actively producing children. So, it seems we might have to wait till we find an answer to the reason of why menopause exists. It is also possible that menopause is just a side effect of long lives of females.

Reference: Whales make waves in the quest to discover why menopause evolved

Non-antibiotics that can act as antibiotics

Antibiotics are medicines that are used to treat infections caused by bacteria. There are other medicines as well which are not antibiotics but have the ability to kill bacteria. This does not mean that they can substitute the traditional antibiotics because these are medicines that are used to treat other conditions. Diabetes medication, non steroidal anti inflammatory drugs like aspirin, antipsychotic medicines are some examples. Although, we know how antibiotics kill bacteria but we do not know how these non-antibiotics work.

Scientists studied 200 non-antibiotics to understand how these drugs interact with bacteria and which genes of the bacteria might be causing their death by a particular drug. What they found was that non antibiotic medicines target the bacteria for killing by following a different path than the antibiotics. This means that the knowledge that we gain from how non antibiotics kill bacteria can be used to develop new antibiotics. During this study, the scientists also found that since the non antibiotic drugs affect the population of the bacteria in the body - mainly the gastrointestinal tract, it may be possible that they contribute towards antibiotic resistance which is when antibiotics are not able to kill bacteria which have become resistant. This particular finding is of utmost importance and needs to be further investigated. Hope the learnings from exploring non antibiotic medicines will help us in combating antibacterial resistance.

Reference: Antibacterial activity of nonantibiotics is orthogonal to standard antibiotics

Are male mammals larger than females?

From the last 150 years, it has been believed that all male mammals are larger in size than females because Darwin said so. Darwin had no proof for saying it. All the studies done so far to look at differences in size of male and female mammals have been biased as they included only a certain type of species, excluding bats and rodents, and relied only on the mean value of the body mass. This current study has challenged the long standing belief of males being larger than females in the mammalian world.

Scientists have now looked at body mass measurements of more than 400 species of mammals. The data that they used for this study included the variance along with the mean values of the body mass. Variance measures how much variation in size exists within a species. The study found that only 45% of the species have larger males than females. And in 39% of the species that were included in the study had no difference in the sizes of males and females. While in 16% of the species, females are larger than males. Thus, although males are larger in most cases when there exists a difference between male and female size in the mammalian world but it is neither universal nor that common as it was earlier thought.

Reference: New estimates indicate that males are not larger than females in most mammal species

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