180 Million Years

In the grand scheme of planetary history, 180 million years doesn’t seem that long. The “big bang” happened sometime between 12 and 14 billion years ago. Between 4 and 500 million years, fungus and plants appeared. Amphibians and reptiles emerged , leading up to the age of dinosaurs at roughly 200 million years ago.

Now ponder this snippet – it wasn’t until 180 million years that species sex was determined by an X or Y chromosome. Not possible you say? How could all those species manage without sexual determination at conception?

Even today many reptiles become male or female based on the temperature of incubation. Alligators whose eggs incubate at 30 degrees Celsius become female, incubation at 33 degrees produce males and temperatures falling in between produce some of each.

Henrik Kaessmann of the Swiss Institute of Bioinformatics published his findings in the journal Nature – tissue samples from mammals, marsupials, and egg laying mammals were studied. They compared genetic sequences of male and females, working backwards as they eliminated similarities. Keeping only sequences corresponding to the Y chromosome. I won’t even pretend truly understanding the science, but will say it’s mind boggling to ponder all those early creatures dependent on temperature for gender.


9 thoughts on “180 Million Years

  1. The immediate thought that came to my ( very unscientific mind) was if the temperature range for determining sex might have been considerably wider in the ”Old Days” and might it have been possible for whole species to have eventually died out if millions of eggs remained one sex ?

    • Good point – one which I don’t have enough information to answer. I can say that scientists are concerned over rising global temperatures today and the possible impact on certain species 🙂

      • They are some of the longest surviving creatures ever to have existed, if my reading about the Dino-Days are correct.
        Surely they are also the top of the pile when it comes to adaptation?

        Aren’t Turtles suffering because of direct depredation by humans rather than temperature change/variation? Just asking.

      • Oh man! Good questions but I’m no expert. My Dino knowledge always assumed they were virtually unchanged for millennia. I had no idea many species of reptiles relied on incubation conditions to determine sex – it truly surprised me. As for turtles – my knowledge ends with an image of giant sea turtle shells floating in the moat of a 16th century Spanish fort in Havana, Cuba.

      • I’m not casting aspersions on the post; I hope to gods you don’t think this? I’m merely throwing stuff in the mix, and you know way more about this stuff than I ever will.

        It would be interesting to know if there are any species that have managed to undergo radical change in a relative short space of time to adapt?

        Lizards can grow tails, yes? Crocs also have some really cool thing’s going for them.
        Aren’t they also being investigated regarding their incredible immune systems?
        Saw something on the telly once?

        I always remember that line in Jurassic Park – ”Nature finds a way” (?)

        The temperature is important for us too, I guess.
        I bloody hate the cold weather. Nothing puts me off more than a cold snap and frost on my slippers!
        If I’d of stayed in England I would never have had kids!


      • There’s a type of grasshopper or cricket in England that has developed actual gears in its leg bones – helps it to jump at ridiculous height and distance to avoid predators (but only when young – after the final moult it looses the gears and hops about like all the other poor bastards Far from on point but the best animal adaptation in a hurry fact I could come up with 🙂

        Don’t ever stop tossing thoughts into the mix – it would be terribly cold without it.

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