I think by now most of us have heard about the idea that women live longer than men -
"Among humans, women's life span is almost 8% on average longer than men's life span."
"In every human population, women live longer than men, so much so that nine out of 10 people who live to be 110 years old are female."
In this thread we will take a look at life expectancies, "aging", and reasons for why women live longer than men not only in humans - but throughout the animal kingdom when focused on mammals specifically -
An introduction:
A new study that looks at lifespan in wild mammals shows that females live substantially longer than males.
The research finds that, on average, females live 18.6% longer than males from the same species.
This is much larger than the well-studied difference between men and women, which is around 8%.
The scientists say the differences in these other mammals are due to a combination of sex-specific traits and local environmental factors.
"The magnitude of lifespan and ageing across species is probably an interaction between environmental conditions and sex-specific genetic variations," said lead author Dr Jean-Francois Lemaître, from the University of Lyon, France.
He gives the example of bighorn sheep for which the researchers had access to good data on different populations.
Where natural resources were consistently available there was little difference in lifespan. However, in one location where winters were particularly severe, the males lived much shorter lives.
Female and Male Bighorn sheep - one has to think the size of those horns on the male bighorn sheep must be extra weight when compared to the female as well as the extra size difference.
My theory:
Larger size and sexual dimorphic traits to lugg around =>
Higher energy requirements =>
bigger likelihood of not being able to find enough resources to supply enough energy especially in stressful conditions =>
higher probability of death when compared to the female
Male animals sexual characteristics help fight off other males and impress females but seems to be a double-edged sword when it comes to the male's own survival ?
"Male bighorn sheep use lots of resources towards sexual competition, towards the growth of a large body mass, and they might be more sensitive to environmental conditions," said Dr Lemaître.
"So clearly the magnitude of the difference in lifespan is due to the interaction of these sex-specific genetics, the fact that males devote more resources towards specific functions compared with females, and to the local environmental conditions."
Even if females lived longer than males, the team found that it did not mean that the risks of dying are increasing more in males than females as they get older. The expected male mortality is always higher, but the rate of mortality is about the same in both sexes as they age.
Let's take a look at elephant seals - one of the largest average age gaps among the animals studied:
We have a male elephant seal on the left and a female elephant seal on the right
Adult males may grow to 14-16 feet (4-5 m) in length and weigh up to 5,000 pounds (2,300 kg). The females are much smaller at 9-12 feet (2.5-4 m) in length and 900-1,800 pounds (400-800 kg). The northern elephant seal is the second largest seal in the world, after the southern elephant seal.
Females generally live for about 19 years, while males only live for about 13 years - a difference of 68.42% in life expectancy - Females come ashore and within a few days give birth to a pup conceived in the previous breeding season.
The nose of the male elephant seal elongates at puberty (7-8 years old) into an inflatable "proboscis." This is used during reproduction when the males establish territories. The territories are established by fighting - both physically (by lunging at each other) and vocally (using their large nose).
Could the male seal's own snout which it uses to impress females and fight off other males and larger size contribute to it's own downfall ?
But what about for humans ? Surely humans can't be one of the only mammals in the entire animal kingdom immune from such things - what is considered dimorphic traits in males that could also be a double-edged sword ?
"
Some examples of sexual dimorphism include differences in stature, weight, morphology of the face, cognitive development, mortality, and disease prevalence. Although humans exhibit low levels of sexual dimorphism compared to other animals, differences between females and males are numerous
"
face ? cognitive development ? stature ?
What could this mean in layman's terms ?
Women seem to prefer taller men, smarter men - AKA - "superior" sexual dimorphic traits
" Males were found to have a larger overall brain volume than women. Studies found that brain volume was between 8% and 13% larger in a man than a woman. "
" The brain is a very expensive organ in metabolic terms. Each unit of brain tissue requires over 22 times the amount of metabolic energy as an equivalent unit of muscle tissue. ... The results show that the increase in brain size in humans is balanced by an equivalent reduction in the size of the gastro-intestinal tract. "
Where are men much taller than women? The following map shows the ratio of male-to-female average heights across the world. Globally, the ratio is 1.07, meaning that on average, men are about 7% taller than women. Across the world, this relative difference between the sexes can vary from only 2-3% to over 12%.
And then of course ... we're all familiar with the saying that short men live longer than tall men
" In 1990, a study of 1679 decreased men and women from the general American population supported these findings. ... Men of height 175.3 cm or less lived an average of 4.95 years longer than those of height over 175.3 cm, while men of height 170.2 cm or less lived 7.46 years longer than those of at least 182.9 cm. "
After all - the tallest men in the world seem to die young of "natural" causes ...
Andre the giant (7"4)- dead at 46
Robert Wadlow (8"11) - dead at 22
John Rogan (8"9) - dead at 37
John Carroll (8"7) - dead at 37
Generally, male skulls are heavier, the bone is thicker and the areas of muscle attachment are more defined than in females. There are also key differences in the appearance of the forehead, eyes and jaw, between men and women that are used to determine the sex of a skull.
...
So then it would seem logical for me to come up with a theory that :
A larger-brained man (smarter man) has more resource requirements than a dumber man - but intelligence is an advantage in fighting off other males and impressing other females
A taller man has more resource requirements than a shorter man - but size is an advantage in fighting off other males and impressing other females
A larger skull with more pronounced sexual dimorphic traits is an advantage in fighting off other males and impressing other females
...
So then if all metabolic conditions are thriving and a man develops stronger sexual dimorphic traits (higher intelligence, larger size, larger skull, etc.)
...
Could this be an advantage in competing with other males and impressing females
BUT
a disadvantage when it comes to increasing the survival rate in the male - creating the right conditions for females to live longer ?
A double-edged sword ?
This is my theory - let me know your thoughts
"Among humans, women's life span is almost 8% on average longer than men's life span."
"In every human population, women live longer than men, so much so that nine out of 10 people who live to be 110 years old are female."
In this thread we will take a look at life expectancies, "aging", and reasons for why women live longer than men not only in humans - but throughout the animal kingdom when focused on mammals specifically -
An introduction:
Mammal study explains 'why females live longer'
Across wild mammal species, females live over 18% longer than males because of genetics and environment.
www.bbc.com
The research finds that, on average, females live 18.6% longer than males from the same species.
This is much larger than the well-studied difference between men and women, which is around 8%.
The scientists say the differences in these other mammals are due to a combination of sex-specific traits and local environmental factors.
"The magnitude of lifespan and ageing across species is probably an interaction between environmental conditions and sex-specific genetic variations," said lead author Dr Jean-Francois Lemaître, from the University of Lyon, France.
He gives the example of bighorn sheep for which the researchers had access to good data on different populations.
Where natural resources were consistently available there was little difference in lifespan. However, in one location where winters were particularly severe, the males lived much shorter lives.
Female and Male Bighorn sheep - one has to think the size of those horns on the male bighorn sheep must be extra weight when compared to the female as well as the extra size difference.
My theory:
Larger size and sexual dimorphic traits to lugg around =>
Higher energy requirements =>
bigger likelihood of not being able to find enough resources to supply enough energy especially in stressful conditions =>
higher probability of death when compared to the female
Male animals sexual characteristics help fight off other males and impress females but seems to be a double-edged sword when it comes to the male's own survival ?
"Male bighorn sheep use lots of resources towards sexual competition, towards the growth of a large body mass, and they might be more sensitive to environmental conditions," said Dr Lemaître.
"So clearly the magnitude of the difference in lifespan is due to the interaction of these sex-specific genetics, the fact that males devote more resources towards specific functions compared with females, and to the local environmental conditions."
Even if females lived longer than males, the team found that it did not mean that the risks of dying are increasing more in males than females as they get older. The expected male mortality is always higher, but the rate of mortality is about the same in both sexes as they age.
Let's take a look at elephant seals - one of the largest average age gaps among the animals studied:
We have a male elephant seal on the left and a female elephant seal on the right
Adult males may grow to 14-16 feet (4-5 m) in length and weigh up to 5,000 pounds (2,300 kg). The females are much smaller at 9-12 feet (2.5-4 m) in length and 900-1,800 pounds (400-800 kg). The northern elephant seal is the second largest seal in the world, after the southern elephant seal.
Females generally live for about 19 years, while males only live for about 13 years - a difference of 68.42% in life expectancy - Females come ashore and within a few days give birth to a pup conceived in the previous breeding season.
The nose of the male elephant seal elongates at puberty (7-8 years old) into an inflatable "proboscis." This is used during reproduction when the males establish territories. The territories are established by fighting - both physically (by lunging at each other) and vocally (using their large nose).
Could the male seal's own snout which it uses to impress females and fight off other males and larger size contribute to it's own downfall ?
But what about for humans ? Surely humans can't be one of the only mammals in the entire animal kingdom immune from such things - what is considered dimorphic traits in males that could also be a double-edged sword ?
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onlinelibrary.wiley.com
"
Some examples of sexual dimorphism include differences in stature, weight, morphology of the face, cognitive development, mortality, and disease prevalence. Although humans exhibit low levels of sexual dimorphism compared to other animals, differences between females and males are numerous
"
face ? cognitive development ? stature ?
What could this mean in layman's terms ?
Women seem to prefer taller men, smarter men - AKA - "superior" sexual dimorphic traits
Men's and women's brains found to be different sizes | NICS Well
“Men really do have bigger brains,” reports the Daily Mail, going on to report that new research reveals “male and female brains are wired differently” with ...
www.nicswell.co.uk
Brains and guts in human evolution: The Expensive Tissue Hypothesis
The brain is a very expensive organ in metabolic terms. Each unit of brain tissue requires over...
www.scielo.br
" Males were found to have a larger overall brain volume than women. Studies found that brain volume was between 8% and 13% larger in a man than a woman. "
" The brain is a very expensive organ in metabolic terms. Each unit of brain tissue requires over 22 times the amount of metabolic energy as an equivalent unit of muscle tissue. ... The results show that the increase in brain size in humans is balanced by an equivalent reduction in the size of the gastro-intestinal tract. "
Human Height
The average height of a population can inform us about the nutrition and living conditions of populations in the past for which we have little other data.
ourworldindata.org
Where are men much taller than women? The following map shows the ratio of male-to-female average heights across the world. Globally, the ratio is 1.07, meaning that on average, men are about 7% taller than women. Across the world, this relative difference between the sexes can vary from only 2-3% to over 12%.
And then of course ... we're all familiar with the saying that short men live longer than tall men
Impact of height and weight on life span - PubMed
The study was conducted to evaluate one aspect of the entropy theory of aging, which hypothesizes that aging is the result of increasing disorder within the body, and which predicts that increasing mass lowers life span. The first evaluation of the impact of human size on longevity or life span...
pubmed.ncbi.nlm.nih.gov
" In 1990, a study of 1679 decreased men and women from the general American population supported these findings. ... Men of height 175.3 cm or less lived an average of 4.95 years longer than those of height over 175.3 cm, while men of height 170.2 cm or less lived 7.46 years longer than those of at least 182.9 cm. "
After all - the tallest men in the world seem to die young of "natural" causes ...
Andre the giant (7"4)- dead at 46
Robert Wadlow (8"11) - dead at 22
John Rogan (8"9) - dead at 37
John Carroll (8"7) - dead at 37
Generally, male skulls are heavier, the bone is thicker and the areas of muscle attachment are more defined than in females. There are also key differences in the appearance of the forehead, eyes and jaw, between men and women that are used to determine the sex of a skull.
...
So then it would seem logical for me to come up with a theory that :
A larger-brained man (smarter man) has more resource requirements than a dumber man - but intelligence is an advantage in fighting off other males and impressing other females
A taller man has more resource requirements than a shorter man - but size is an advantage in fighting off other males and impressing other females
A larger skull with more pronounced sexual dimorphic traits is an advantage in fighting off other males and impressing other females
...
So then if all metabolic conditions are thriving and a man develops stronger sexual dimorphic traits (higher intelligence, larger size, larger skull, etc.)
...
Could this be an advantage in competing with other males and impressing females
BUT
a disadvantage when it comes to increasing the survival rate in the male - creating the right conditions for females to live longer ?
A double-edged sword ?
This is my theory - let me know your thoughts