To add comments or start new threads please go to the full version of: Prehistoric Species Size And Gravity Change
PhysForum Science, Physics and Technology Discussion Forums > General Sci-Tech Discussions > Creation / Evolution

light in the tunnel
I'm aware that this is yet another crank idea, but I'm posting it anyway for explanations why it's impossible.

Basically, I wonder if the reason why species (plant and animal) have evolved in the direction of smaller organism size. I wondered if it could be the result of changing gravity as the core cools and settles, resulting in a decreasing radius between gravitational center and crust-level. I don't even know how to estimate how much this radius might have decreased through time, and I question whether the change in gravity would be that significant, but I can't rule it out yet either.

If gravity was less, I would think that plants and trees would be able to grow taller due to easier water transport. I don't know if cells themselves would grow larger as a result of lower gravity. I think that increasing gravity would cause species to evolve smaller since larger individuals would be more susceptible to broken bones and hunger than smaller ones. Of course, such evolution could still occur without any change in gravity - but only as a result of competition and accidents.

Still, I don't think there is a similar reasoning as to why plants would have evolved smaller. The only thing I can think of is that bigger plants may require more nutrients and richer soil, which they contribute to by dying and decomposing, so as soil becomes depleted, smaller plants may be more likely to survive to reproduce.

Any thoughts?
buttershug
The biggest problem is that animals tend to evolvel to be bigger.
Untill conditions become unstable (like after a major asteroid strike) and then the small more adaptable animals survive.
orestis
Dumb ***. Trying to show compassion to you is a waste of time.

Why don't you research before you post stupid questions. Are you trying to impress with what you think are brilliant insights?

Ask wikipedea, you will learn about gas ratios and food supplies on islands.
keith*
QUOTE (light in the tunnel+May 5 2010, 04:28 PM)
...Basically, I wonder if the reason why species (plant and animal) have evolved in the direction of smaller organism size... Any thoughts?

search: "species shrinkage cause"
light in the tunnel
Found a BBC article linking species shrinkage to warmer climates. I'd actually heard that before, since the ratio of surface area to volume is higher in smaller animals and lower in larger ones, allowing the larger ones to dissipate less heat per unit volume.

As for whether I'm trying to impress with brilliant insights; thanks for the compliment but the truth is that I once would have been afraid to even talk openly about these kinds of thoughts out of fear for coming across like I was doing exactly what you say. Now I just don't care enough about my ego to worry about portraying myself as a humble person.

I'm not posting this idea to boast. I just find it interesting and I wanted to see what others had to say. I don't get why buttershug thinks that species evolve to be bigger. What would some examples be? Prehistoric horses may have been smaller; but sloths, tigers, elephants/mammoths, etc. were larger. This could be explained by climate warming since the most recent ice age, but what about fish and other sea animals, not to mention insects?
buttershug
Dinosaurs were pretty darn big. Until something happenened.
Sabertooth tigers and woolly mammoths were pretty big until something happened.

Don't just look at todays animals and say "they are smaller therefore they evolved smaller". If that were the case, then where da heck did the big animals come from in the first place?

Herbivores tend to evolve bigger then predators evolve bigger, as long as there is stability for millions of years. But when an asteroid hits or continents join together the stability is lost.
light in the tunnel
QUOTE (buttershug+May 6 2010, 10:38 AM)
Dinosaurs were pretty darn big. Until something happenened.
Sabertooth tigers and woolly mammoths were pretty big until something happened.

Don't just look at todays animals and say "they are smaller therefore they evolved smaller". If that were the case, then where da heck did the big animals come from in the first place?

Herbivores tend to evolve bigger then predators evolve bigger, as long as there is stability for millions of years. But when an asteroid hits or continents join together the stability is lost.

I think a high rate of biomass-production is needed to fuel food-chains of larger animals. I think bigger plants are necessary that grow faster, for herbivores. I suspect that the emergence of land species could have resulted in a long period of "prosperity" since plants had already evolved, presumably, and the animals that survived on land could proliferate without encountering shortages, I assume.

The question I'm stuck on is what caused the plants to be larger? Lower gravity would allow for easier water-transport to a higher altitude with the same energy. What else could explain larger and/or faster plant growth?
buttershug
A few large animals would not need bigger faster plants than lots of small animals.
And the atmosphere makes a bigger difference than an incredibily small change of gravity.
light in the tunnel
QUOTE (buttershug+May 6 2010, 03:50 PM)
A few large animals would not need bigger faster plants than lots of small animals.
And the atmosphere makes a bigger difference than an incredibily small change of gravity.

So what caused the plants to be bigger then? More CO2 in the atmosphere? Was the nitrogen cycle different? You don't think water-transport plays a role in limiting plant size?
flyingbuttressman
QUOTE (light in the tunnel+May 7 2010, 12:14 PM)
So what caused the plants to be bigger then? More CO2 in the atmosphere? Was the nitrogen cycle different? You don't think water-transport plays a role in limiting plant size?

Plants like lots of sunlight, lots of water, and rich soil. The amount of CO2 present suggests that a strong greenhouse effect was in place, so temperatures were probably higher. Higher heat means more humidity, which means more water for the plants. I believe that there was also a period of heightened Volcanism during that point, which means rich, fertile ash in the soil.
Lasand
litt;

This is not quite what you are wondering. You might find it interesting anyway.

"Dirac proposed that the universal gravitational constant G, is related to the age of the universe."

http://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis
Lasand
Anyway, in my opinion, the earth won't experience the likes of the Brontosaurus again.
light in the tunnel
QUOTE (Lasand+May 7 2010, 05:49 PM)
litt;

This is not quite what you are wondering. You might find it interesting anyway.

"Dirac proposed that the universal gravitational constant G, is related to the age of the universe."

http://en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis

I googled it but I don't quite get the idea. Is it that the overall mass of the universe is decreasing as it ages, so there is an average level of gravity that would be decreasing as well?

I have been thinking about the quality of spacetime between stars or between galaxies, but it is not really related to this thread. In this thread I was thinking more about the possibility that the Earth is condensing as it settles and expels energy and gases. This is why I thought prehistoric sea-level might be at a much higher altitude than it currently is.

The thing I wonder about with the spacetime between stars and between galaxies is whether it continues to dilate until it reaches a "plateau" or whether there might be areas of deep space where it actually contracts again for some reason. Actually, the reason is not "for some reason." It is related to my (crankish) idea that the energy emitted by stars may actually propel them higher in the spacetime topography.

Typically I would think of spacetime as a fabric dented with gravity wells of stars, planets, black holes, galaxies, etc. But because I've had this idea that energy counteracts gravitation, it seems like the gravity wells of the stars could be like craters at the top of a mountain/volcano, figuratively in terms of spacetime topography, I mean. This doesn't really make any sense unless there is some mass creating the "valley" that deep space would be, but maybe there is some base-level of spacetime dilation/contraction/density external to that created by mass.

I suppose the best way to describe this idea would be that spacetime fabric would be elastic and tend to contract in the absence of energy to expand it. So the relatively dilated spacetime surrounding a star would be the product of the stars energy output, and as that energy dissipates at farther distances from the star, spacetime itself would tend to re-contract to its baseline density, which I guess would be like how it was prior to the big bang.

This is extreme crank speculation, but it would somewhat explain the appearance of an expanding universe in that light would be slowing down in the contracted spacetime, or put another way, light would have a long path to follow down and back up the deepening valleys in the spacetime topography. In fact, gravity itself might be nothing more than the tendency for spacetime to contract in the absence of energy, which dilates or expands it.

Hopefully I won't get ridiculed to badly for continuing to explore my crank ideas, but I at least feel like mentioning it since it seems somewhat related to this idea of a gravitational constant of the universe.
PhysOrg scientific forums are totally dedicated to science, physics, and technology. Besides topical forums such as nanotechnology, quantum physics, silicon and III-V technology, applied physics, materials, space and others, you can also join our news and publications discussions. We also provide an off-topic forum category. If you need specific help on a scientific problem or have a question related to physics or technology, visit the PhysOrg Forums. Here you’ll find experts from various fields online every day.
To quit out of "lo-fi" mode and return to the regular forums, please click here.