Lack of Females May Have Done in Dinosaurs

Oddy Enough - Reuters ^ | 2004-04-21

[Junior]

WASHINGTON (Reuters) - An asteroid may have wiped out the dinosaurs 65 million years ago not simply by changing the world's climate and causing years of dark skies, but also by causing too many of them to be born male, U.S. and British researchers say.

If dinosaurs were like modern-day reptiles such as crocodiles, they change sex based on temperature, David Miller of the University of Leeds in Britain and colleagues noted Tuesday. And even a small skewing of populations toward males would have led to eventual extinction.

Most experts agree that one or more asteroid impacts probably triggered a series of global changes that killed off the dinosaurs and many other species of life on Earth. The impacts would have kicked up dust that cooled the air and also triggered volcanic activity that would have created even more dust and ash.

No one really knows if dinosaurs were more like reptiles, or something closer to mammals. Reptiles have very different metabolisms than mammals and also have various ways of determining the sex of offspring.

In mammals, if a baby gets an X and a Y chromosome, it will be male and if it gets two X chromosomes it will be female, with a few very rare exceptions. Similar mechanisms work for birds, snakes and some reptiles such as lizards.

But in crocodilians, turtles and some fish, the temperature at which eggs are incubated can affect the sex of the developing babies.

Miller's team ran an analysis that showed a temperature shift could theoretically have led to a preponderance of males. Other studies have shown that when there are too few females, eventually the population dies out.

"The earth did not become so toxic that life died out 65 million years ago; the temperature just changed, and these great beasts had not evolved a genetic mechanism (like our Y chromosome) to cope with that," said Dr. Sherman Silber, an infertility expert in St. Louis who worked on the study.

But crocodiles and turtles had already evolved at the time of the great extinction 65 million years ago. How did they survive?

"These animals live at the intersection of aquatic and terrestrial environments, in estuarine waters and river beds, which might have afforded some protection against the more extreme effects of environmental change, hence giving them more time to adapt," the researchers wrote.

 

[Junior]

Ping.

[dirtboy]

Miller's team ran an analysis that showed a temperature shift could theoretically have led to a preponderance of males. Other studies have shown that when there are too few females, eventually the population dies out.

Then one would expect that all reptilians would have died out, and not just dinosaurs.

[Junior]

I would have though so, too. Fortunately, the good doctors answered the question at the end of the piece:

But crocodiles and turtles had already evolved at the time of the great extinction 65 million years ago. How did they survive?

"These animals live at the intersection of aquatic and terrestrial environments, in estuarine waters and river beds, which might have afforded some protection against the more extreme effects of environmental change, hence giving them more time to adapt," the researchers wrote.

[Republicus2001]

No, no, no, no. Its BushFault

[GraniteStateConservative]

They had women. They just had headaches too often. It also didn't help that the male dinosaurs answered wrong when asked by the female if her hips were too wide.

[Alouette]

It wasn't that there were too few females, it's just that too many dinosaurs were gay.

[kallisti]

what? all the female ones were aborted?

[JohnnyZ]

Then one would expect that all reptilians would have died out, and not just dinosaurs.

I'm assuming you didn't read the whole article:

But crocodiles and turtles had already evolved at the time of the great extinction 65 million years ago. How did they survive?

etc.

[GoredInMich]

Yep. Either that, or the far left factions of reptiles allowed for homosexual T-rex's, stegasaurus, and brontos to marry each other......the rest is history...as they say.

[NCPAC]

Lack of females would do me in, too.

[No Blue States]

There was one female left, the males jumped off very high cliffs trying to impress her.

[dirtboy]

I disagree with the accessment. Crododilians, after all, lay their eggs out of water and rely on the sun to incubate them.

My take on the extinction of the dinosaurs? It wasn't an extinction. Megafauna dinosaur forms died out, but birds, the small fauna form of dinosaurs, survived and thrived, and mammals took over the megafauna niches.

[Tallguy]

2 problems with this theory:

1. Current data suggests dinosaur physiology to be more like that of modern birds, and
2. Large reptiles, like crocodiles, survived.

I think that I remember seeing a program where a major paleontologist commented on the declining diversity amoung dinosaur species BEFORE the asteriod impact event 65 million years ago. I guess that science writers can't get past their disaster-theory -- Just easier to sell to us poor, dumb, ignorant masses.

[Eric in the Ozarks]

Liberals, like the dinosaurs they are, often eat their young.

[glock rocks]

Either that, or the far left factions of reptiles allowed for homosexual T-rex's

All T-rex's look gay. I mean, what's up with those arms?

[Verginius Rufus]

Other studies have shown that when there are too few females, eventually the population dies out.

A brilliant insight, right up there with "When people are out of work, unemployment results."

[William Terrell]

Feminists beware: lack of practicing females might doom the human race.

[No Blue States]

All T-rex's look gay. I mean, what's up with those arms?

ROFL!!!

Man thats funny.