Dave Hone: belief

Transcript context

…Because you have the population data, so you can… …You can ask them a lot more questions. And we can treat it as a population. So going way, way back to a conversation about telling males and females apart, and I said the big problem is population data, or at least the number of specimens that you have when mostly you’ve only got one, two, or three. I did a big study on this a few years ago on gharials, the really long-snouted crocodilians from Nepal, India, and Pakistan with a giant bulge on the end of the nose. And even though the males are all bigger than the females, and the males all have this weird nose growth that’s mostly soft tissue, but they have a weird depression in the jaw, in the end of the snout where the nostrils sit. We got a sample size of something like about 110 animals, so these are very, very rare animals, so we had to ransack every museum worldwide. I was sending my students sending emails to huge numbers of people, “Have you got one sitting in your collection lost? Can you get it for us? Can you take these photos or these measurements? We can measure it. ” We put the dataset together, and then we found that actually, apart from the very biggest males, it’s really hard to tell males and females apart, and this actually really closely matched some modeling data that I’d done with a colleague, Jordan Mallon in Ottawa looking at this for alligators and trying to compare it to dinosaurs. Because though we talked about mutual sexual selection before, neutral sexual selection in particular, you tend to get things that are extremely similar. Males and females are very hard to tell apart. But there’s also a gradient, you know, all the way up to things like peacocks, all the way down to you can’t tell them apart, like parrots. And for some features, when they take time to get growing, or because dinosaurs grow over a very long window and are sexually mature over a very long window, you run into the problem that a big female will look like a small male. And we can’t sex them. And lo and behold, this is what you get with the gharials. The really big males are obvious because they’re so much bigger and they’ve got this big depression in the snout. But medium-sized and big females look like medium-size or smaller males and very small males. And so, yeah, that’s basically what we have with dinosaurs. Even with Protoceratops, where we’ve got a dataset of like a hundred, papers have come out saying there’s very mild sexual dimorphism or there isn’t sexual dimorphism. Sexual dimorphism could be very strong in Protoceratops, but we can’t find it because we can’t tell the males from the females because we haven’t ID’d enough through something like medullary bone. And so you’re in this horrible situation where, because going back to the T-Rex thing, it’s like, “Well, maybe it’s mutual sexual selection, and therefore they’re cooperating,” and that would be cool. But also, maybe males are much bigger, but we can’t tell because our dataset’s too small. Oh, that’s frustrating.…

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