Why were plants and animals larger millions of years ago?

Question

I am currently having a debate with someone who believes the earth is growing and that is has in fact doubled in size in the last 65 million years and that because the planet was smaller it had less gravity and this is why the plants and animals were larger, what is the real scientifically accepted theory?

Answer 1

Plants and animals were not larger in the past. Most of the fossils that we find are tiny, even microscopic. At the time of the dinosaurs, mammals were mostly shrew- or mouse-sized. Some dinosaurs were large, most were small or mid-sized.

I don't know where your friend is getting his information but the source is either ignorant or disingenuous.

Answer 2

The largest Animal that ever lived is still around now! (the blue whale)

http://www.bbc.co.uk/nature/wildfacts/fa...

"The blue whale is the largest animal ever to have lived - bigger, even, than the dinosaurs. Yet they are elusive creatures, and little is known about their lives."

Answer 3

I'm not sure, but your friend's theory is complete bull. Smack them

Answer 4

no!

the reason that the size of insects has changed is due to oxygen levels - the higher the oxygen level - the larger the insect

as for the size of the planet - it's eroding and growing all the time - but not to the extream your friend suggests!

animals are the optimal size for their environment

Answer 5

From Wikipedia:

"The theory has a relatively small following today, compared with the almost universally accepted theory of plate tectonics, and is considered to be discredited by mainstream geologists. Many of those that remain are proponents of the ideas of the late Australian geologist S. Warren Carey. While Carey's ideas were popular for a time in the 1950s and 1960s, most workers in earth science believe that evidence collected over the last several decades supports a fixed size Earth, due to subduction, over the expanded Earth."

In short, your friends ideas are incorrect, and discredited. Though there are still websites that push this belief, there are websites that push geocentricism.

Answer 6

there wasn't no rock to hit the earth .

Answer 7

Plants were no necessarily bigger. However, some insects and animals tended to gigantism; and one possible reason for this is that there was a higher concentration of oxygen back then (by the way, and for the record, there also were small dinosaurs; it is not because there are elephants living today that mouse sized mammals cannot exist; except that one has to admit that mouse sized dinosaurs do not leave very large fossil to recover). Today, our atmosphere is 21% oxygen, back then it could have been about 30%. As to where that extra oxygen went, one possibility is that it got fixated by the burning of all the plants that died following the meteor impact that wiped out the dinosaurs.

As for this rather silly gravity change (where the heck would that extra mass come from?) it can easily be dismissed by analyzing dinosaur bones: they were meant to support current gravity; they would have been much limber if gravity had been less.

Answer 8

Ermmm I doubt it, and I thought they were larger because they had large landscapes to go around and had a lot of food.

Answer 9

It's a flipping good question! I'm not sure why, but I just wanted to throw in that I heard on Walking With Dinosaurs (or similar) that some animals were smaller - apparently horses were the size of dogs - eeek!!!! So it's a mixed bag!

Answer 10

because when time goes by, things change, like the earth, you see the earth has gotten hotter so everything has changed, thus making it need that animals ad plants change, and thats natural humans do it all the time, we adapt to our different surroundings, for example if your in a dessert in africa your going to need special cloths, but in a ice storm your als going to need a lot of cloths! hope i helped

Answer 11

they had more fast food choices - meaning more 99 cent menus -  than we do these days.  

Answer 12

Ask him why he thinks humans have gotten progressively taller.