The recent African origin of modern humans, frequently dubbed the “Out of Africa” theory, is the most widely accepted model describing mankind’s geographic origin and early migration. The theory asserts that humans first evolved in Africa, and most of man’s time on earth has been on that continent.
Here are six reasons why scientists believe humans originated in Africa and why they have abandoned the notion we evolved separately and independently in different parts of the world.
1. Nature Doesn’t Strike Twice
There exists two theories of human origin: monogenism and polygenism. The monogenic view, which today is referred to as the “out of Africa theory,” states that there is one source for mankind; man was born in one place but evolved differently due to the climatic conditions to which he was exposed.
The polygenic theory, or multiregional origin of modern humans, claims that man has several locations of origin, which would explain the physiological differences between the races. Followers of this theory believe that man was born in Africa, Europe and Asia, and there was no evolutionary or climatic development.
World renowned historian, anthropologist, and physicist Dr. Cheikh Anta Diop states one important reason why the polygenic theory is faulty is that Mother Nature never strikes twice; she doesn’t create the same being twice.
2. The Oldest Human Fossils Are Found in Africa
According to Diop, the fossils of early humans who lived between 6 million and 2 million years ago come entirely from Africa, and no such fossils have been found anywhere else in the world. Also the fossils found outside Africa are a lot more recent.
The February 2008 issue of National Geographic News says that genetic studies and fossil evidence show modern humans originated in Africa about 250,000 years ago. Relics of Homo sapiens idaltu found at site Middle Awash in Ethiopia, lived about 160,000 years ago. It is the oldest known modern human and classified as an extinct subspecies.
3. Africans Have The Oldest DNA
Two pieces of the human genome have proved useful in deciphering human history: mitochondrial DNA and the Y chromosome. These are the only two parts of the genome that are not shuffled about by the evolutionary mechanisms that generate diversity with each generation. Instead, these elements are passed down intact.
According to the “Out of Africa” hypothesis, all people alive today have inherited the same mitochondria from a woman who lived in Africa about 160,000 years ago. She has been named Mitochondrial Eve. All men living today have inherited their Y chromosomes from a man who lived 140,000–500,000 years ago, probably in Africa. This man is known as the Y-chromosomal Adam.
4. Africans Have The Most Diverse DNA
A May 2002 study by researchers at the University of Chicago’s Department of Ecology and Evolution, examined three groups of people, Africans, Europeans, and Asians. The researchers found greater genetic diversity among Africans than among Eurasians, and that genetic diversity among Eurasians is largely a subset of that of Africans. Because there is no other similar center of genetic diversity outside of Africa, the DNA evidence supports the “Out of Africa” model.
Another study in July 200 by the University of Cambridge, England, found that the lowest genetic variation was found in ancient populations from South America and Australia, the two main inhabited regions most remote from Africa.
Andrea Manica, the team’s lead, concluded, “The more you move away from that center of diversity where you started, the less diversity you have.”
The study places the original roots of modern humans in south-central Africa. In the middle of this region lies the Great Rift Valley—often referred to as the “cradle of humanity.”
5. Migration Patterns
The genographic project displayed on the National Geographic website reports that when humans first ventured out of Africa some 60,000 years ago, they left genetic footprints still visible today.
By mapping the appearance and frequency of genetic markers in modern people, researchers can create a picture of when and where ancient humans moved around the world. These great migrations eventually led the descendants of a small group of Africans to occupy even the farthest reaches of the Earth.
The earliest people to colonize the Eurasian landmass likely did so across the Bab-al-Mandab Strait separating present day Yemen from Djibouti. These early beachcombers expanded rapidly along the coast to India, and reached Southeast Asia and Australia 50,000 years ago.
The first great journey of humanity beyond Africa had led Africans all the way across the globe.
6. Chinese Scientist Proves Original Chinese Were Africans
In 2005, a Chinese DNA specialist, Jin Li, leading a team of Chinese and other scientists from the University of Texas in Houston, proved through DNA tests that the first inhabitants of China were indeed Black Africans, who migrated across Asia in a southeasterly direction before heading north into what is now China.
This challenges the long-standing view of Chinese paleontologists, based on fossil evidence, that an East Asian branch of Homo erectus independently evolved into Homo sapiens.
“It is now probably safe to conclude that modern humans originating in Africa constitute the majority of the current gene pool in East Asia,” said Jin.