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Holy shit and I thought it couldn't get worse
On an evolutionary level, the finger flick of choice in the human mating game is often influenced by subconscious input from our most primal instincts.
In females, hormones present at ovulation can drive a woman to choose more masculine features. Men can sniff out an ovulating woman just by smelling her T-shirt, while women appear to prefer the smell of a man with dissimilar genes, which could give her offspring a boost up the evolutionary ladder.
A fascinating new study finds those chemical-based preferences continue even after sex. New research from Stockholm University, Manchester University NHS Foundation Trust and The University of Manchester shows that eggs use chemical signals to “choose” which sperm will become the lucky winner in conceiving a baby.
Once the sperm makes it up to the fallopian tube and meets the egg, it comes into contact with chemoattractants in the follicular fluid.
The researchers found it is likely the strongest sperm survives but merely because the egg chose to have that happen.
"Human eggs release chemicals called chemoattractants, which leave a sort of chemical breadcrumb trail that sperm use to find unfertilized eggs", said study author John Fitzpatrick.
“What we didn’t know until this study is those chemical breadcrumbs act differently on sperm from different males, in effect choosing which sperm is successful,” Fitzpatrick added.
Sperm, as it turns out, have odor receptors in their heads that respond to the chemoattractants in the egg's follicular fluid. When sperm go into the fluid, they start to go straighter and they start to change the way they swim. So, depending on the strength of that signal, you can get different responses in how the sperm are responding to these female chemical signals within their follicular field.
What this is suggesting is that these fluids are giving females one extra chance — long after she’s picked their partner — to bias the number of sperm that are going to be coming toward the eggs.
And here’s the extraordinary finding: A woman’s egg doesn’t always agree with her choice of partner.
"We expected to see some sort of partner effect, but in half of the cases the eggs were attracting more sperm from a random male". The most likely explanation for this is that these chemical signals allow females to choose males who are more genetically compatible.
If the egg likes the sperm, it sends chemical signals that tell it to swim faster. However, if the egg doesn't like the sperm, the signals it sends encourage the sperm to slow down. It's the proper law of attraction at work, with the egg actually ghosting the sperm it's not interested in.
And because mammals, including humans, are programmed to give our offspring the best chance for survival, our bodies have developed all sorts of methods to reward the strongest, most diverse and compatible mate possible. Even the female reproductive tract is an obstacle course designed to weed out weaker, less acceptable suitors.
Reproductive tract fluids, for example, flow downwards, thus forcing sperm to swim upstream, much like salmon must do when they spawn. At the same time, Fitzgerald said, the female’s immune system views sperm as a foreign invader, attacking those swimmers as if they were germs. Once past the obstacle of the cervix’s muscular contractions, sperm must then choose and swim up one of two fallopian tubes — yet the egg only travels down one, leaving a “blind alley that they can go down where there’s no payoff.”
The journey is so arduous that of the tens of millions of sperm a male might deposit, our best estimate is that only about 250 total sperm get to the site of fertilization where the egg is.
On top of all of that, only about 10% of the 250 sperm are able to fertilize at any given time — they sort of blink on and off in their capacity to fertilize eggs. So of that 250, it’s more like 20 or 30 cells that can actually fertilize an egg at any different time.
“And it’s only in the last two centimeters between a sperm and the egg that these chemical signals matter since it’s the final phase of this long journey where females continue weeding out less acceptable sperm,” Fitzgerald said.
On an evolutionary level, the finger flick of choice in the human mating game is often influenced by subconscious input from our most primal instincts.
In females, hormones present at ovulation can drive a woman to choose more masculine features. Men can sniff out an ovulating woman just by smelling her T-shirt, while women appear to prefer the smell of a man with dissimilar genes, which could give her offspring a boost up the evolutionary ladder.
A fascinating new study finds those chemical-based preferences continue even after sex. New research from Stockholm University, Manchester University NHS Foundation Trust and The University of Manchester shows that eggs use chemical signals to “choose” which sperm will become the lucky winner in conceiving a baby.
Once the sperm makes it up to the fallopian tube and meets the egg, it comes into contact with chemoattractants in the follicular fluid.
The researchers found it is likely the strongest sperm survives but merely because the egg chose to have that happen.
"Human eggs release chemicals called chemoattractants, which leave a sort of chemical breadcrumb trail that sperm use to find unfertilized eggs", said study author John Fitzpatrick.
“What we didn’t know until this study is those chemical breadcrumbs act differently on sperm from different males, in effect choosing which sperm is successful,” Fitzpatrick added.
Sperm, as it turns out, have odor receptors in their heads that respond to the chemoattractants in the egg's follicular fluid. When sperm go into the fluid, they start to go straighter and they start to change the way they swim. So, depending on the strength of that signal, you can get different responses in how the sperm are responding to these female chemical signals within their follicular field.
What this is suggesting is that these fluids are giving females one extra chance — long after she’s picked their partner — to bias the number of sperm that are going to be coming toward the eggs.
And here’s the extraordinary finding: A woman’s egg doesn’t always agree with her choice of partner.
"We expected to see some sort of partner effect, but in half of the cases the eggs were attracting more sperm from a random male". The most likely explanation for this is that these chemical signals allow females to choose males who are more genetically compatible.
If the egg likes the sperm, it sends chemical signals that tell it to swim faster. However, if the egg doesn't like the sperm, the signals it sends encourage the sperm to slow down. It's the proper law of attraction at work, with the egg actually ghosting the sperm it's not interested in.
And because mammals, including humans, are programmed to give our offspring the best chance for survival, our bodies have developed all sorts of methods to reward the strongest, most diverse and compatible mate possible. Even the female reproductive tract is an obstacle course designed to weed out weaker, less acceptable suitors.
Reproductive tract fluids, for example, flow downwards, thus forcing sperm to swim upstream, much like salmon must do when they spawn. At the same time, Fitzgerald said, the female’s immune system views sperm as a foreign invader, attacking those swimmers as if they were germs. Once past the obstacle of the cervix’s muscular contractions, sperm must then choose and swim up one of two fallopian tubes — yet the egg only travels down one, leaving a “blind alley that they can go down where there’s no payoff.”
The journey is so arduous that of the tens of millions of sperm a male might deposit, our best estimate is that only about 250 total sperm get to the site of fertilization where the egg is.
On top of all of that, only about 10% of the 250 sperm are able to fertilize at any given time — they sort of blink on and off in their capacity to fertilize eggs. So of that 250, it’s more like 20 or 30 cells that can actually fertilize an egg at any different time.
“And it’s only in the last two centimeters between a sperm and the egg that these chemical signals matter since it’s the final phase of this long journey where females continue weeding out less acceptable sperm,” Fitzgerald said.
