:confused: This one has driven me mad for years and this recent discovery hasn't helped

'Scientists found evidence in Scotland of a water scorpion that was 5.2 feet long and about 3.2 feet wide. The monster lived about 350 million years ago.'

My questions are simple - why were animals in the distant past so large? If being big was such an advantage, why have we so few relatively large animals living now? Large animals take a long time to get big, did they grow faster than now or did they protect their young from predation? Is gravity a variable? Was it less in the past??

Your question is a good one... and has not been answered.

Some say that it had to do with the food quality - and some say it was a defense against predators.

... both are guesses.

I found 49 hits for webpages with that question; and it looks about half and half for the two theories aka guesses:

http://www.google.com/search?hl=en&q...=Google+Search

When you look at things, not all dinosaurs were big. Life started small, and as time went on and the world become poplulated with life. What is happening is how well they adapt to their surrounds and how evolution changes them. The Earth's climate is always changing in order for the animals to survive they need to adapt. I do like to point out that not all dinosaurs were big. Most of the fossils I work with come from small dinosaurs, although we do find sauropods. They were among the last living dinosaurs close and after the KT boundary. You're two guess are right, and I do agree with Rick that we don't really know all the answers, we have the evidence but research like this takes time science is best understood based on theories. But theories are changed a lot.

Some of these ancient creatures such as Dimetrodons had large sail like sheets of skin on their backs which help to regulate their temperature during the extremely hot days and freezing cold nights.

Lavina,what a lucky person you are,in the job that your doing.Is it true that dinosaur skin colour was just a guess,as no one really knows for sure,except to say,that they would have to blend in with the natural background?
Secondly,after "that meteor/comet" smashed into the Gulf of Mexico,and oblitorated 90% of land-life,small birds survived,and small rodents.The only sea creatures left,were crocs,alligators,whales,et al.So in other words,small "life" survived,where as poor old dino died through global freezing,and a lack of food,due to no photosynthasis (lack of sunlight)?
ProjManRaz,that is the question of the forum.Good one.

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Originally Posted by ProjManRaz

:confused: This one has driven me mad for years and this recent discovery hasn't helped

'Scientists found evidence in Scotland of a water scorpion that was 5.2 feet long and about 3.2 feet wide. The monster lived about 350 million years ago.'

My questions are simple - why were animals in the distant past so large? If being big was such an advantage, why have we so few relatively large animals living now? Large animals take a long time to get big, did they grow faster than now or did they protect their young from predation? Is gravity a variable? Was it less in the past?????

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Good question, and, to be honest, I don't know why some animals, both past and present, are so large. However, I do know that the average size of a dinosaur was that of a sheep, and that ain't all that big.

Phil Debenham

Actually the biggest animal to ever have lived is alive today. The blue whale. A better way to ask is why lizards aren't as big as their progenitors. I suppose the answer is that they don't need to be. I know that is not a complete answer but it certainly starts one to wonder.

It is because all they had to do, is hunt and eat ,as they were the largest animal on earth then ,it wasn't dificult for them to get food. Due to this their body size increased ,but note that the brain size didn't increase... big body and small head... to think

This the main cause of their extinction that they anly knew to eat and eat and go on eat... while how to keep them extant couldn't help,because they couldn't think of it... this is because at that timethe morphology of earth was undergoing changes ,both chemical and radiational changes,due too much irridium activity they were all killed and extinct... because they couldn't think of a better solution to the problem... see they didn't have good quality of brain to think that if there is a lot of irridium and raidation in the air they could have dived with a spook of air pipe underwatre in water bodies to keep safe... :) this is jjust to make you explain that they couldn't think well how to keep themselves safe and lively.

Let me know if it helped, I have taken a course in this subject ,so I have tried to explain in a best possible way.

Some believe it was because there was a higher content of oxygen in the atmosphere (evidence in fossilized resin of conifer trees indicates O2 was 35% at one time, compared to only 21% now). As well, there may have been a higher atmospheric pressure. As a result, the blood absorbed more O2, allowing the species to grow much bigger

The oxygen content explanation might be a factor but there were some pretty huge mammals running around just 10,000 years ago - many of them much bigger than their counterparts today. Got to think that predator relationships had to play some kind of very major role.