Tuesday, October 22, 2002

How this Missing Mass of The Universe Killed the Dinosaurs Part I of II

I first published this in the newsgroups several years ago. Recent findings on dinosaurs have continued to support my theory, so I thought I would share this original version, and then add my firther speculations.

How this Missing Mass of The Universe Killed the Dinosaurs Part I of II

by brad@elstore.com

Speculation has fallen so far out of fashion in these post-modern times, that I want to be sure to warn you that what follows is not a scientific theory. Instead, it is a series of logical suppositions that seem to hang together in explaining a very puzzling event in the history of life. I apologize to any serious scientists who find themselves reading this. I am really writing for the general public, for entertainment and as an example of philosophical speculation.

I have absolutely no credentials in any of the fields I am discussing. However, these ideas are so much fun, I wanted to share them with you. I hope you enjoy this exposition as much as
I enjoy writing about it.

We know that dinosaurs and mammals developed at about the same time in the history of life on Earth. Dinosaurs were much more successful than mammals, and expanded to fill many environmental niches, both on land and in the oceans, and eventually in the sky. Then some great change occurred, and the dinosaurs disappeared from the land and the oceans, and only survived in the air, as birds.

It has become a modern myth that the dinosaurs were killed by a large meteor strike 66 million years ago, that created a worldwide winter that froze the dinosaurs to death. This theory
suits our genetic pride, in that we are descended from the animals that were smart enough to grow their own fur coats, but it really doesn't make sense. What about the dinosaurs in the
sea? If it were cold enough for the seas to freeze over, it would have been so cold that all of the land animals, including mammals, would have frozen solid. What about the reptiles and the
amphibians, who certainly would have perished in the same catastrophe if it had occurred?

While many species died out, only the family of dinosaurs disappeared completely.

So the 'Big Chill' theory, that the dinosaurs were frozen out of the evolutionary parade, has to be abandoned.

I have a different idea. It's an idea that is based on a logical analysis of the existing facts, and it leads to some suggestions for future study.

We know that dinosaurs had an advantage over mammals at one time, and lost that advantage. Whatever was their advantage, became their detriment.

We tend to think of dinosaurs as animals that had a certain physical structure, but we must remember that they really had a certain biology. The structure really existed to take advantage
of the biology.

The earliest protodinosaurs were small, bipedal, high-speed hunters. The last dinosaurs, who became birds, were adapted in some ways to the same environment that produced the mammals.

The fact that all of the dinosaurs, in completely different environments, die at about the same time, has led some to speculate that there was a sudden case of 'dinosaur influenza'
that killed off everyone with a certain genetic structure. This idea is attractive because it answers the nagging question how anything could so specifically target a certain section of the
animal kingdom.

However, I think there is a simpler and more satisfying answer.

Let's go back to the time when dinosaurs and mammals developed. The Earth is warmer, the temperature is more uniform, and the atmosphere is full of oxygen from photosynthesis. I think at that point, the first dinosaurs developed based on a metabolic advantage. The dinosaur had a high-energy metabolism based on taking advantage of the high oxygen content in the air. I think the atmosphere was significantly denser than it is now. Even if the percentage of oxygen were the same as it is today, the partial pressure of oxygen would be higher. This means that there is more oxygen available through respiration, if you have the metabolism to handle it.

Meanwhile the mammals are developing for a very specific environmental niche. Mammals develop hair, warm blood, live birth, and suckling of their young, to exist in a colder environment. That cold environment is on mountains. Everywhere else is pretty warm, but high altitudes have lower temperatures - and thinner air.

The dinosaurs have the metabolic advantage almost everywhere, except on mountaintops. Since the air is denser, the rate at which the air becomes thin, is higher. There is a much more rapid drop-off in pressure as you gain altitude. The dinosaur's special adaptation to high oxygen availability is a liability in thin air. So the dinosaur family tree expands to fill most of the world, the seas, and eventually they reach for the skies.

Some of the dinosaurs begin to evolve, into two different kinds of birds.

Meanwhile a major astrophysical event is coming up. The signature of this event, is the meteorite strike, the KT event, that we think somehow killed off the dinosaurs.

That somehow is by changing an environmental condition worldwide. It can't be rainfall, since dinosaurs in the sea died also. It can't be temperature, because anything extreme enough to kill
every dinosaur would kill all the reptiles also, and probably the fish, birds, amphibians, and mammals. The only other variable is air.

Something happened to make the air thinner. Dinosaurs, that had a metabolism dependent on high oxygen availability, died everywhere. Those that didn't die immediately lost their metabolic advantage over other animals.

Mammals, of course, are already adapted to lower oxygen environments because they developed in high altitudes.

Highflying birds make it through the environmental sieve. Ground-hugging birds, that are not adapted to thin air, die out.

So the mammals take their turn at family expansion, and replace the dinosaurs on land and in the oceans.

(I call this The Last Gasp Theory). I think that evidence for this theory can be found, perhaps in the geologic record, and perhaps in the mitochondrial and unexpressed chromosomal DNA of
birds. It would not surprise me to find 'fossil DNA' in birds that would show this metabolic capability. (I suspect there is fossil DNA of all kinds in complex animals. Recombine it in a
certain way and you might get a stegosaurus, for example.)

What could change the atmospheric pressure so rapidly?

The most obvious candidate would be a near miss by an asteroid, moon, or comet. My next suggestion is that interstellar space is full of planetary-sized bodies, and that our companion planets (and probably the Earth itself) did not form in the vicinity of the sun.

The recent evidence of planets orbiting nearby stars has been exciting and a little unnerving. Most of the planetary systems we have evidence of, have large planets, larger than Jupiter,
orbiting very near to their star. It's obvious in the case of some of them, that the planet could not have formed at that distance from the star, if it is anything like the large planets we know of in our own solar system.

The measurement methods we have are primitive, and can only pick up nearby planetary systems with massive planets near the star. These are probably unusual and relatively temporary situations (with the planet eventually being eaten by the star, or moving
farther from the star). The fact that there are so many nearby planetary systems that we can detect, even though we can only detect unusual ones, suggests that virtually every star has
planets. We don't know if these other systems are 'normal', and our apparently more stable system is the strange duck, or vice versa.

The prevailing hypothesis about our solar system is that the planets developed in place, attendant on the sun. I think of this as 'the Divine Right of Rings' theory, where you explain that things must be so because that is the way that they are.

In our solar system, the outermost members are the most eccentric in their orbits. Some people consider Pluto to be a captured comet. I think all of the planets are captured comets.

I am not surprised to see the recent evidence that Jupiter must have formed farther from the Sun. (This is based on the prevalence of noble gasses in the atmosphere of Jupiter.)

Comets are considered to be bodies that have been disturbed from their home in the Ort Cloud, a hypothesized ring of debris beyond the orbit of Pluto. They come zipping around the sun in long elliptical orbits.

Of course, if one of those comets should be the size of a large rotating planet, tidal forces affecting that giant comet as it passes around the sun, over and over again, would ten to make the orbit more and more spherical. In the end, you would have a planet in a conventional orbit around the sun. Of course this might take a billion years or two.

So a solar system consists of material that has collected in the space between the stars, gradually being brought inward to the nearer orbit around the sun. This material, in the form of
comets, planets, asteroids, tends to decelerate and fall into the sun over time. The reason for this deceleration is either gravitational interaction with other bodies in orbit, or outright
collisions between bodies.

You can see the effect of this in the asteroid belt, the collection of thousands of small micro planets between the orbits that has been falling into the sun for billions of years.

In other planetary systems, it seems that even Jupiter-sized planets are spinning inward to the star.

If there is anything unique about our solar system, it is in the stability of the orbits of the planets.

(continued in part II)