[Home] [Headlines] [Latest Articles] [Latest Comments] [Post] [Sign-in] [Mail] [Setup] [Help]
Status: Not Logged In; Sign In
|
Science/Tech See other Science/Tech Articles Title: What can killer whales teach us about the menopause? The menopause is a puzzle for biologists. Why would the female of a species cease to reproduce half way through her life, when natural selection favours characteristics that help an individual's genes survive? A study of killer whales - one of only two mammals apart from humans to undergo the menopause - is providing clues. Granny is very spritely for a centenarian. When I finally catch sight of San Juan Island's local celebrity, she leaps clear out of the ocean to delighted gasps from everyone on my boat. Granny is a killer whale, or orca. She lives in a coastal area of the North Pacific, close to Vancouver and Seattle, known as the Salish Sea. And while she is affectionately known as "Granny", her formal name is J2 - an alpha-numeric title that identifies her as a member of a population known as the Southern Resident orcas. It is a clan of 83 killer whales in three distinct pods - J, K and L-pod - all of which return to this area of coastal Pacific waterways every summer. The network of inlets and calm inshore sea is peppered with forested and mountainous islands. Its beauty makes it popular with tourists - especially whale-watchers. What many camera-clasping visitors want most is a glimpse of Granny - the oldest known living killer whale. Her age is an estimate, based on the age of her offspring when she and her pod were first studied in the early 1970s. She is at least 80, scientists say, and could be as old as 105. I am here with a team of biologists who have a particular interest in her. They want to understand why J2, and the other females of this population, stop having babies in their 30s or 40s, even though they live so much longer. Biologists call it post-reproductive lifespan. We call it menopause. Only three known mammals experience the menopause - orcas, short-finned pilot whales and we humans. Even our closest ape cousins, chimpanzees, do not go through it. Their fertility peters out with age and, in the wild, they seldom live beyond childbearing years. But female orcas and women evolved to live long, active, post-reproductive lives. Image caption Prof Darren Croft (right) with Ken Balcomb from the Center for Whale Research "From an evolutionary perspective, it's very difficult to explain," says Prof Darren Croft, who travels here from the UK's University of Exeter to study the whales. "Why would an individual stop having their own offspring so early in life?" Darwinian evolutionary theory says that any characteristic reducing an animal's chance of passing on its genes to the next generation will be edged out - the process of natural selection. That has led some to argue that menopause in humans is a result of longer life, better health and better medical care. But, as well as painting a rather depressing image that post-menopausal women are simply alive beyond their evolutionarily prescribed time, that theory has been largely debunked - thanks, in part, to these orcas. Obviously, medical care is not increasing their lifespan. "So studying them in the wild could help us reveal some of the mystery of why menopause evolved," Croft says. He and his fellow researcher Dr Dan Franks from the University of York, are investigating whether older post-reproductive females increase the survival chances of the rest of their family, and therefore of their own genes. One part of their research is to plug the whales' vital life statistics - birth rates, death rates and odds of survival - into a Darwinian calculator to see if menopause is a net benefit. It is a biological cost-benefit analysis. The question is whether an older female brings a measurable benefit to her existing family which outweighs the genetic cost of having no more babies. Find out more You can listen to Victoria Gill's documentary The Whale Menopause here - it was first broadcast on BBC Radio 4 But Croft and Franks also watch, very closely, how the killer whales behave. Some of their latest insights came from analysing hundreds of hours of video footage of the whales going about their lives - chasing the salmon on which they depend for sustenance. "We noticed that the old females would lead from the front - they're guiding their groups, their families, around to find food," says Croft. Crucially, he and Franks also noticed that the older females took the lead more often during years when salmon supplies were low - suggesting that the pod might be reliant on their experience, their ecological knowledge. "It's just like us," says Croft. "Before we had Google to ask where the shop was, if there was a drought or a famine, we would go to the elders in the community to find out where to find food and water. "That kind of knowledge is accumulated over time - accumulated in individuals." Jump media player Media player help Out of media player. Press enter to return or tab to continue. Media captionThe killer whales struggling to feed themselves As we stand on the small research boat, Croft points out two dorsal fins, emerging briefly, like glistening black sails, from the surface of the water. They belong to a mother and an adult son, who appear to be working together to catch fish. "That's an adult son, a 23-year-old male, staying right by his mother's side," Croft says. His calculations have revealed just how much adult males depend on older matriarchs for their survival. "From observations that had been collected on the whales, it appeared that the sons were dying shortly after their mothers died - they were being called 'mummy's boys'," he says. "So we looked at the [survival] data and found that if a mother dies, the risk of death of her sons is around eightfold the following year. "And these are not immature males - these are 30-year-old, fully grown sons. She's doing something that's keeping those sons alive." A mother killer whale's sons and daughters remain in her pod throughout their lives, and while the males leave briefly - to mix and mate with other females - they return, and are often seen swimming at their mother's side. There have even been observations of older females sharing fish with their sons - literally feeding these full-grown "mummy's boys" with salmon. So older females, it seems, work very hard to support their families, particularly their adult sons. This makes good Darwinian sense, Croft argues. Sons mate with females from other pods, so those calves are the matriarch's genetic grandchildren, but it's a different pod that has the extra mouth to feed. Image copyright Alamy Image caption Hadza women in Tanzania with a child There is also evidence from the few remaining human hunter-gatherer societies that older females help their children, and their children's children, survive - a phenomenon dubbed the "grandmother effect". University of Utah anthropologist Kristen Hawkes, who has studied the Hadza people of northern Tanzania since the 1980s, has observed how older women are particularly industrious, and spend more time foraging for their families than younger women. "Kids in this Hadza hunter-gatherer population are also surprisingly active foragers at very young ages, but - as in all human populations - they can't fully feed themselves when they are weaned and still depended on food supplied by their mothers," she says. "But when mothers had a new baby - the weaned youngsters depended on grandmothers. So we saw grandmothers' subsidies in action in those people, that would have likely operated in ancestral [human] populations." Rather than foraging for regular sustenance, Hadza men go after big game, and when they make a kill, they share it with the whole community. "Everybody comes to join in eating the mountain of meat," says Hawkes. "So most of it goes not to their own wives and kids but to others." Post Comment Private Reply Ignore Thread Top • Page Up • Full Thread • Page Down • Bottom/Latest Begin Trace Mode for Comment # 2.
#1. To: Ada (#0)
60 MINUTES once aired an episode about The Mamonis of Italy-grown men who still rely on their mothers to iron their shirts, prepare their meals and relieve them of the responsibility of marriage, allowing them the freedom to operate as VESPA gigolos instead. The Mamonis have their own residences but it's not too much trouble to show up for meals and carry their laundry over to Mom!
In the US today an astonishing number of children are in their grandmother's care.
#3. To: Ada (#2)
Don't I know it. A former employer, husband and wife team had a daughter with a baby girl, and the daughter was not capable of (or interested in) raising a child. It didn't bother her when the state took temporary custody of the little girl, until her parents finally did. It was clear that the daughter simply wanted to do drugs, have sex and be free of any consequences for same. And she didn't care who had the baby as long as it wasn't her.
Top • Page Up • Full Thread • Page Down • Bottom/Latest |
||
|
[Home]
[Headlines]
[Latest Articles]
[Latest Comments]
[Post]
[Sign-in]
[Mail]
[Setup]
[Help]
|
||