[Jill & Chris]

Jill & Chris  asked the Naked Scientists:
   
Hello Scientists,

My question is too long to be asked on the radio, it is possible that the answer will be a short one, lets see:

As a 12 year old child I stood alongside the dinosaur skeleton in the Natural History museum in London, totally dwarfed by its enormity.   It left a lasting impression on me (I am now 70) and gradually over the years I have developed a feeling of dissatisfaction with the common representation of dinosaurs running amok amongst smaller creatures and crashing through vegetation; I cannot reconcile that with the weight (estimated) of the larger dinosaurs, up to 80,000 kgs.   I also am aware that no tracks of a dino tail have been found longside their footprints, indicating that their muscular control must have
been extraordinary.

With the weight of our largest living land animal, the elephant being only approx 12,200kgs it seems inconceivable that the dinosaurs
could even move, let alone run. Basically the elephant is a lumbering creature, except when enraged, but its weight is only a small percentage, (15%) of that of the dinosaur.

So my questions are:
How on earth did they move at all?
Was gravity different in some way during their time?
Was the atmosphere so different then that it allowed such creatures to exist?

A spin question: (Sorry) Did man's evolution therefore only begin 65million years ago?  I believe that everything was wiped out except life underground or in water - seems a comparatively short time considering our complexity.

I guess you will come back with an answer that will shoot my gravity idea down in flames, but I cannot, at this point, conceive a different solution.

Thank you for the immediately accessible, unbelievable knowledge you pass on every week on Radio 702 - addictive listening.

Kind Regards

Jill Dimmer
Johannesburg

What do you think?

[geo driver]

the atmosphere was different. there was a higher level of oxygen.. i think this allowed the dinos to grow bigger. i think it was 30% oxygen as opposed to 20% today.

gravity was no different

they had extremely well developed muscles (pure conjecture but i think its right)

and i believe small mammals were around 65 million years ago.

also not that long ago there were giant sloths which were the size of an elephant, were talking 200-400 years ago. perhaps all this is from memory which for me is foggy at best

[ornate iridescence]

Mammals were evolving alongside the dinosaurs, and share a common ancestor with dinosaurs. When the dinosaurs became extinct, they left behind habitats and resources, so the mammals evolved explosively to adapt and exploit the opportunities.

The first primates appeared around 60 million years ago (mya).
Great apes (the group of primates that includes us) appeared between 18 and 12 mya. The Human lineage diverged from the Chimpanzee lineage about 6 mya. Anatomically modern humans arose about 200,000 years ago. Behaviourally modern humans arose at least 50,000 years ago.

[JimBob]

We can do the physics of the weight bearing ability of dinosaur bones. We can also tell from the muscle scars on the bones - the places where the muscles attach - how big the muscles were. Using the ability of modern muscles as a comparison, the ability of the dinosaurs to move can be determined. This is how we know that the dinosaurs could move - just as we can tell before putting up a skyscraper that it will  be able to stay up. The physics is the same for animals as for buildings.

The mega-fauna geo-drive refereed to dies out as late as 10,000 years ago. 

[geo driver]

my memory is really foggy sorry for the error. but cheer for the correction was i roght on the oxygen levels though

[Don_1]

As has been said, fossil evidence shows how powerful their muscles would have been. But they were probably not the strongest creatures to have inhabited Earth. An ant is capable of lifting 10 times its own weight. If I could do that, I would be able to lift over a ton!
DOH!!! What a giveaway.

[JimBob]

was i roght on the oxygen levels though

Roight-o gov

[geo driver]

50% right then makes a change normaly im 100% wrong

[chrisrich]

An ant is capable of lifting 10 times its own weight. If I could do that, I would be able to lift over a ton!
DOH!!! What a giveaway.

Many ants can lift more.  Even up to 50 times their own weight.  Frightening little creatures they are.