Due to the vast differences in the text books on the probable time period that early man entered North America, I used a broad date (40,000 to 9,000) to indicate the Paleo period. Many text books cite that there is no evidence of human habitation before 13,000 in North America and other sources state that there is some evidence dating back 15,000 years ago. Many archaeologists, anthropologists, and other scientific minds theorize that man could have existed in North America as far back as 40,000 years ago. This is due to the fact that there were several major shifts in the ice age at the time. It is theorized that the land bridge from Siberia to Alaska (called Beringia) was visible and walkable three different times from 40,000 to 10,000 years ago and man could have migrated at any or all these times. The Native Americans or American Indians history probably began some 40,000 years ago. This is the earliest known date that evidence of man was found in North America. During this time the ice age was fully in swing and an ice bridge linked Asia with North America. The theory today is that the ancestors of the American Indians were actually mongoloids. The evidence is overwhelming to this fact. The scant beard, prominent cheekbones, striaght black hair, broad face, large torso, short legs, dark brown-red skin, and a tendency to slanted eyes.