Were dinosaurs already having a hard time before the asteroid hit during the Late Cretaceous?
I was linked an article this morning by a friend of mine from I Fucking Love Science, or IFLS for short, talking about the recent findings of dinosaur's population decrease before the asteroid impact. The research they're referencing, was published to Proceedings of the National Academy of Sciences by Manabu Sakamoto and others, and talks about their research into tracking the decline of four major species groups before the k-2 extinction event: Sauropods, Theropods, Hardosaurs and Ceratopcians.
I remember hearing that the population of dinosaurs was in a decline before the asteroid before, but to be honest I wasn't up to speed on the latest research when this was linked to me this morning. I remember reading The Dinosaur Heresies by Dr. Bakker when I was a kid, and he had brought up this theory of dinosaur's population slipping because of mass sickness.
Even as a kid that theory seemed a little too much, and to be very fair there has been newer findings after he had published that book.
Since I was in the dark about the newest research around this topic, I set off to do some digging in science papers.
Why would I go digging through science papers if IFLS already told me the "in-a-nutshell" summery of the findings?
IFLS aside, most online media sources are bullshit and garbage, who over sensationalize the facts for more clicks, especially when it comes to science.
More on that later. Let's get to the meat of the research, shall we?
- Population Decline within Niche Groups:
Summery from published research:
Whether dinosaurs were in decline before their final extinction 66 Mya has been debated for decades with no clear resolution. This dispute has not been resolved because of inappropriate data and methods. Here, for the first time to our knowledge, we apply a statistical approach that models changes in speciation and extinction through time. We find overwhelming support for a long-term decline across all dinosaurs and within all three major dinosaur groups. Our results highlight that dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event 66 Mya.
If you want to read the actual article published by the research team, it is actually 100% free and available here.
I love that this paper wasn't behind a paywall, because I could see what the actual research team published. This is an actual science paper, so it is complicated and dry, but the info is all there which is fantastic.
Like I stated before IFLS did a good bare-bones article about it that is simple to read, as did phys.org.
The research team tracked four species through the Mesozoic using the "Bayesian Phylogenic approach" to study their evolution and speciation decline.
I know what you're asking...whaaat the hell is Bayesian Phylogenic approach? I know I asked that too, and I had to Google it.
According to wikipedia (yeah, I know, not the most reliable source but whatever):
Bayesian inference of phylogeny uses a likelihood function to create a quantity called the posterior probability of trees using a model of evolution, based on some prior probabilities, producing the most likely phylogenetic tree for the given data. The Bayesian approach has become popular due to advances in computing speeds and the integration of Markov chain Monte Carlo (MCMC) algorithms. Bayesian inference has a number of applications in molecular phylogenetics and systematics.
So, basically it's an algorithm to determain evolution and speciation trees, which is really cool.
The researchers used this model to plug in the data of these groups into the Bayesian trees and were able to tract the decline in evolution among the species. Basically, the niches they filled didn't leave a lot of room for change, so species were starting to die off without new ones filling in the gaps. From what I understand of the data, they piqued and started to slow down in evolution and diversifying.
This seems to be happening across the board, which all the major groups starting to fall before the mass extinction event that pushed them over the edge.
I guess when you evolve to be these giant beasts that are beyond the scale of anything else that has ever lived on the planet, you certainly can't get any bigger and evolution doesn't work backwards. Eventually you'll get too big and start to run into snags in getting food and diversifying, especially when the planet was a hostile mess during that time. I mean of course the tons of volcanic activity and shifting plates during that time which would have made planet Earth a bit nasty.
Poor guys were having a hard time as it was, then a giant rock came down and made everything a lot worse. With the species already rocky in diversifying, they certainly couldn't make it through a huge event that leveled the playing field for the smaller animals. Those that had grown into those giant niches didn't have a strong leg to stand on and weren't going to last long as giant behemoths as it was.
- Why I had to Dig:
I don't know if anyone remembers the article that was floating around on the internet a couple months back about the pregnant t-rex that was found recently. This was an amazing find because of the correlation between the female t-rex bones and that of a pregnant bird, which helps shine some light in more of the t-rex's breeding habits and helps with sexing the bones found.
Instead of publishing this information, many sites ran with ridiculous headlines like "Dino DNA found in Pregant T-Rex!", which was never, ever stated by the research team.
The publishers of the article ran with one quote from one of the researchers, Lindsey Zanno, when they asked her if there could be DNA in the bones:
"Yes it is possible....but this remains to be tested further."
This had nothing to do with the true excitement of the findings, and instead the media ran through the streets with sparklers screaming bullshit to get more people to click on the page. I guess if they headlined it as "new data found to help properly sex dinosaur bones" only people who wanted to know about proper paleontology techniques and those who want to see bones doing it would have clicked.
I'm a very skeptical person as it is, and I rarely take anything at face value when it comes to anything on the internet, but having to do that much digging to make sure what was being said on online news outlets wasn't full of crap is tiring. We were lucky their findings wasn't behind a paywall, or having to pay to get access to the article, like so many science papers are. It leaves us to the whim of the media outlets, which typically don't have our best interests in mind. They don't want to present the facts purely, they want to make us excited and get views.
It's sad and gross.
Like I stated before, this isn't all news outlets and there are plenty who do a great job outlining what's going on. The unfortunate truth is that most of the general public doesn't go to PLOs One or Phys.org...they go to Huffington post, The Guardian, CNN and so on, who aren't science news sources. They take the information and boil it down to what sells and pepper in some data.
We have a very real problem with science illiteracy in this country, and it boils my blood to see it spreading by lazy or sensationalized reporting.
- TL;DR
Certain dinosaur species weren't evolving fast enough to keep up with niche die-offs and speciation had slowed down.
You can read the published paper here.
Don't believe everything you read on the internet, do your own research. In this case it wasn't so bad, but it has been in the past.
Yay dinosaurs!
Thanks, guys.
-M
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