"All living things except plants are members of the animal kingdom," it was explained. "Except for birds and mammals, all members of the animal kingdom are cold-blooded. Warm-blooded animals do not depend on external temperatures to maintain a constant body temperature. Instead, they have evolved sophisticated physiological mechanisms that control internal heat production." 

Humans had been classed as "members of the mammal group." One scientist remarked, "Humans, like all other primates, are essentially tropical creatures. We have been able to expand our living range because of cultural adaptations. But given their druthers, people prefer warmer climes." 

In a human being, it was said, "the temperature is about 98 and a half degrees on the average. It may be half a degree less, or half a degree more, and it still will be 'normal'. In a single day it is normal for the blood to change up to one degree. It is lower in the early morning, and higher in the early evening. If a person's temperature rises 2 degrees above average, or falls 2 degrees, it is well for him to have the advice of a doctor." 

It was noted humans "have managed to cope with cold by cleverly adopting some of Mother Nature’s techniques. We wear coats of fur and jackets of down (described as an extremely effective insulating material), and we've managed to build all kinds of warm shelters. Some people would probably like to sleep through most of the winter, but so far this notion – along with the grey seal’s penchant for developing a thick layer of blubber – hasn’t developed a following." 

It was pointed out, "Man is the only specie of land-living mammals which does not have a full coat of body fur for protection from temperature extremes." 

In 1984 it was reported "scientists may have learned the secret of the polar bear's ability to lie about contentedly on ice floes. It turns out that each hair in this Arctic denizen’s thick fur coat has a nearly hollow core. Scientists now believe that the core might act as a kind of 'light pipe', or solar cell, transmitting energy absorbed from the sun into the bear's hide." 

"All mammals start developing as females," it was mentioned, "even those that inherited a male sex chromosome from the father. The genetically male mammal embryos have one ‘X' and one 'Y' chromosome. Genetically female embryos have 2 'X' chromosomes." 

And finally, "Extinction is a natural event. New species can’t come in until old ones go out. The rule is still competition of the most efficient creatures."

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