ANIMAL SIZES

Eric writes...

Enough with the atomic questions and here's a new category. Is there an anatomical reason why LAND mammals aren't able to reach such enormous proportions like the dinosaurs did?

There is an anatomical reason that land mammals don't grow to the size of dinosaurs. We have growth plates on the ends of our bones that limit the length that they will grow. The growth plate, also known as the epiphyseal plate or physis, is the area of growing tissue near the end of the long bones in children and adolescents. Each long bone has at least two growth plates: one at each end. The growth plate determines the future length and shape of the mature bone. When growth is complete, sometime during adolescence, the growth plates close and are replaced by solid bone. This, of course is preprogrammed by our genes.

Some animals seem to keep growing for as long as they live. Fish for example will keep growing, however, the growth in length decreases every year. According to the Alabama Department of Natural Recourses, a largemouth bass in an Alabama reservoir will, on average, grow to 6.9" in one year, 10.6" the second year, 13.3" the third, 15.4" the fourth and 17.2 the 5th. This growth, again, is determined by it's genes. Fish will also grow to their environment. Put a goldfish in a small fishbowl and it will remain small. Put it in a large tank and it will grow larger, but you can put it in a swimming pool and it's size is still going to be limited.

We might want to ask the question "Is there and evolutionary reason that animals were so much larger during the age of the dinosaurs than they are today?" I researched that and I came up with many theories, many of them conflicting each other, and none of them without gaping holes in them. Of all the theories, the ones that seemed the most credible to me deal with the change in environment. Oxygen and radiation levels have changed. Weather and temperatures have fluctuated. Species have changed, therefore, both food sources change and the competition for those food sources change. Dinosaurs may have had more oxygen, better weather, more food sources, and less competition than animals have today.