Extinction of the dinosaurs according to Lovejoy

I'm nearly finished with Lucy, but before I close the book I thought I would share Owen Lovejoy's hypothesis about the extinction of dinosaurs as related by Don Johansen. Keep in mind that the book was first published in 1982 when ideas about what killed the dinosaurs were legion;

[Also, for some of the terminology here to make sense, organisms are sometimes referred to being r-selected or k-selected in terms of their reproductive strategies. A r-selected organism produces lots of offspring with little investment in each, like corals that release egg & sperm in great quantities. Fertilized eggs will then drift through the ocean and may or may not find a spot to settle, but the sheer quantity of them means there's a chance at least some of them will find a place to live. A k-selected organism, by contrast, produces fewer offspring but puts a bigger investment into that offspring. A good example would be the African elephant, a mother carrying one calf for a long time and caring for it for a long time once it leaves the womb.]

What dinosaurs did as parents, no one knows, although some of them, on the evidence of clutches of fossil eggs found in the Gobi Desert, were certainly stingy egg producers; some "nests" contain only a dozen or two. Thus, if dinosaurs were no better parents than most other reptiles, they would have been losers in two ways: "r"-care, "K"-oriented in their tendency to lay small numbers of eggs. That could explain their extinction in a world that was beginning to fill up with "K"-oriented mammals that were better parents.

"You don't have to look for sunspots, climatic upheavals or any other weird explanation to account for the disappearance of the dinosaurs," said Lovejoy. "They did fine as long as they had the world to themselves, as long as there was no better reproductive strategy around. They lasted more than a hundred million years; humans should as well. But once a breakthrough adaptation was made, once dinosaurs were confronted by animals that could reproduce successfully three or four times as fast as they could, they were through."

Although the "Dinosaur Renaissance" was in full spring when this hypothesis was published, Johanson & Lovejoy's notion rests on the idea that dinosaurs were just big lizards. According to the idea reproduced above, dinosaurs were not prolific enough to drown out the ever-increasing hordes of mammals, nor were they good enough parents to protect their young from mammals with a taste for baby dinosaurs, and so our distant relatives took down the saurian empire from the ground up.

It makes for an ok story, but nothing of the sort happened. Mammals and dinosaurs were not in direct competition with each other for "dominance of the world," and while some mammals did eat baby dinosaurs, there was no breakthrough moment in which the mammal population exploded, eating dinosaurs out of house and home. What's more, dinosaurs did not simply drop a dozen eggs in the ground and walk away; they provided at least as much care for their young as modern crocodylians and birds do, and so the "death by mammal" hypothesis falls flat.

Tags

More like this

Whether they're referred to as hot flashes, power surges or personal summers, the experience of menopause is not fun. But could it be the result of human evolution? One of the most fascinating areas of research in evolutionary studies is the question of reproductive senescence. Why do women go…
Fossils demonstrate beyond any doubt that Mesozoic dinosaurs laid eggs, as of course do all dinosaurs today. But back during the 1960s, 70s and 80s - back when Robert Bakker and his idea about dinosaur biology were regularly featured in magazines and other popular sources - the scientific…
This is one beautiful plesiosaur, Polycotylus latippinus. (Click for larger image) (A) Photograph and (B) interpretive drawing of LACM 129639, as mounted. Adult elements are light brown, embryonic material is dark brown, and reconstructed bones are white. lc indicates left coracoid; lf, left femur…
In January 2011, Junchang Lü, David Unwin, Charles Deeming and colleagues published their Science paper on the amazing discovery of an egg-adult association in the Jurassic pterosaur Darwinopterus (Lü et al. 2011) [the specimen is shown here: image courtesy of Junchang Lü, Institute of Geology…

No disrespect to Dr. Johanson, but wasn't the Maiasaura Egg Mountain site known at this point?
It was long before my time (1979, I believe). Does anyone know if that find was popular in the presses during the early '80s?

By Adam Pritchard (not verified) on 06 Apr 2008 #permalink

Well, being a mammal, allow me to say I like my Triceratops eggs over easy. With some Steggo Bacon on the side.
And the last time I was in Denny's, I would swear that both the server, and the toast were left over from the early Triassic.