Fred Flynn: Gigantism in the ancient world occurred in the kingdoms of the insects, plants and animals. It has long been a mystery and topic of conjecture: why were these living things so big, and why not now? Dragon flies with 60 cm. wingspans, dinosaurs, such as the brontosaurus, that surely must have caused the earth to shake as they moved about searching for food and evading predators were the standards for those distant days.
I've never heard that before. Interesting but it doesn't explain how a brontosaur would have kept his neck up or how a giant insects exoskeleton could have supported it's wieght. The alternative explanation which does explain this is the expanding earth theory. If in the past the earth was smaller the gravity would have been less.
Uranium has a half life of 4,5 Billion years. Dinosaurs lived in an era (geologically speaking) that ended some 130 million years ago, way before man, but the levels of background radiation from Uranium deposits are largely the same as today.
Radioactive mutations are not dependent on environmental conditions, the DNA gets screwed producing many , many deviant organisms which may arise, but they simply cannot survive.
The premise from the article is that background radiation led to a huge variety of organisms achieving gigantism this is a fallacy, because Gigantism in this respect can only survive if there is sufficient protein resource to sustain it.
You need to be looking at other mechanisms for an answer to the Gigantism during the Jurassic, and cretaceous periods. Might be better to look at gas concentrations in the atmosphere, climatic conditions etc because high levels of radioactive particles would not affect each organism in the the same way and produce viable "giants" without other influences..
p.s. "Brontosaurus" became "Apatosaurus" many, many years ago because it was incorrect.
Humankind has only been around for a million years give or take, but as the planet's dominant species we're too getting bigger and bigger by the century, radioactivity not required. Fuel (food, oxygen) grew the dinosaurs big, and ironically their massive energy requirements made them all dead as environmental catastrophe wouldn't allow adequate fuel for creatures as large as dinosaurs to survive. Abundant food sources are certainly required to sustain giants like dinosaurs or whales yet there would still be substantial environmental constraints on population sizes due to their enormous size. Mammals had much lower energy requirements to subsist and so rose to global prominence. I would guess there is a very high correlation between population growth rates of a species and increases in that species' average body mass through time.
Without going out of my door
I can know all things of earth
Without looking out of my window
I could know the ways of heaven
Posted 04 September 2012 - 11:38 AM
Ryegrog, on 02 September 2012 - 05:48 AM, said:
Agreed. We're much bigger and taller then our ancestors 100 years ago. So maybe dinos had plenty to eat.
I do remember reading somewhere it has got to do with abundance of food and climate, but if you look at Homo Heidelbergensis this fellow averaged 1.8 [6.0ft] to 2.13 [7.0ft] tall and a lot more muscular then modern humans so anything is possible.