Out-of-Africa Theory: The Origin Of Modern Humans

Big Picture First species of Homo, Homo habilis, likely evolved in Africa around 2 million years ago. First species of Homo, Homo habilis, likely evolved in Africa around 2 million years ago. Later, a descendant of Homo habilis, Homo erectus likely evolved (along with other hominids), and spread out of Africa. Later, a descendant of Homo habilis, Homo erectus likely evolved (along with other hominids), and spread out of Africa. Homo erectus likely gave rise to Homo sapiens 100,000 to 200,000 years ago. Homo erectus likely gave rise to Homo sapiens 100,000 to 200,000 years ago.

Two Main Theories Out of Africa Theory – suggests that Homo erectus evolved into Homo sapiens in Africa, and then ventured out of Africa and dispersed to all around the world. Out of Africa Theory – suggests that Homo erectus evolved into Homo sapiens in Africa, and then ventured out of Africa and dispersed to all around the world. Multi-regional Evolution Theory – suggests that Homo erectus ventured out of Africa and then evolved into modern man in several different locations through out the world. Multi-regional Evolution Theory – suggests that Homo erectus ventured out of Africa and then evolved into modern man in several different locations through out the world.

Genetic Tools to Find the Answer Fossil records Fossil records DNA sequencing DNA sequencing –Mitochondrial DNA analysis (mtDNA) Maternally inherited, therefore telling the story from the female side of human history Maternally inherited, therefore telling the story from the female side of human history –Y Chromosome analysis Inherited down the paternal line, complementing the mtDNA Inherited down the paternal line, complementing the mtDNA

Polymorphisms Polymorphism - Existence of a gene in several forms. Polymorphism - Existence of a gene in several forms. Polymorphic regions provide a very unique set of genetic markers for studying human origin and migratory patterns. Polymorphic regions provide a very unique set of genetic markers for studying human origin and migratory patterns. Used to construct a global evolutionary tree of modern man Used to construct a global evolutionary tree of modern man

The discovery was announced in the online journal eLife on September 10, South Africa, offers evidence of a previously unknown branch of the genus Homo. Skeletons show feet and hands similar to living humans, combined with high shoulders, broad pelvis, ribcage; curved finger bones hint at the importance of tree-climbing in this bipedal group typical of Australopithecus, the likely ancestor of Homo. Since this combination of traits is unknown it’s given a new species name – Homo naledi. A view of all of the 1,550 Homo naledi fossils from the Rising Star Cave

Mitochondrial DNA Out-of-Africa hypothesis was first sketched out in 1987, based on mitochondrial DNA analysis Out-of-Africa hypothesis was first sketched out in 1987, based on mitochondrial DNA analysis Suggested that modern man first appeared on the scene in eastern Africa about 150,000 years ago, and left between 35,000 and 89,000 years ago, eventually conquering the globe. Suggested that modern man first appeared on the scene in eastern Africa about 150,000 years ago, and left between 35,000 and 89,000 years ago, eventually conquering the globe.

The figure shows the endocast of a Homo erectus brain (blue) superimposed on that of a Homo sapiens (red), aligned horizontally on the brain stem under the cerebellum (C), and vertically along the bottom margin of the temporal lobe (T).

Y Chromosomal DNA Study Researchers looked at DNA samples from 12,000 male Y chromosomes in Asia. Researchers looked at DNA samples from 12,000 male Y chromosomes in Asia. Looking for 3 specific mutations on the Y chromosome known to have originated in Africa. Looking for 3 specific mutations on the Y chromosome known to have originated in Africa. Researches found that every one of the 12,000 samples carried one of the three mutations Researches found that every one of the 12,000 samples carried one of the three mutations

More Y Chromosomal Studies Samples were taken from men in 22 different geographical areas. Samples were taken from men in 22 different geographical areas. –In countries that included Pakistan and India, Cambodia and Laos, Australia and New Guinea, America, Mali, Sudan, Ethiopia and Japan. Researchers identified 167 polymorphic markers on the Y chromosome. Researchers identified 167 polymorphic markers on the Y chromosome. Markers were then assembled into 10 types, called haplogroups. Markers were then assembled into 10 types, called haplogroups.

Conclusion to the Y Chromosome Study Little or no interbreeding of Homo erectus and Homo sapiens. Little or no interbreeding of Homo erectus and Homo sapiens. Individuals are descendants from Africa Individuals are descendants from Africa Likely that the early African man emigrated to North Africa and made the leap to Asia and then to the rest of the world. Likely that the early African man emigrated to North Africa and made the leap to Asia and then to the rest of the world. Indicates that modern humans of African origin completely replaced earlier populations in East Asia. Indicates that modern humans of African origin completely replaced earlier populations in East Asia.

Findings from Y Chromosomal Analysis Assembled a phylogenetic tree showing a migration from eastern Africa into the Middle East, then southern and southeast Asia, then New Guinea and Australia, followed by Europe and Central Asia. Assembled a phylogenetic tree showing a migration from eastern Africa into the Middle East, then southern and southeast Asia, then New Guinea and Australia, followed by Europe and Central Asia. Some modern day men in Sudan, Ethiopia and southern Africa are the closest lineal descendants to the first Homo sapiens who left Africa Some modern day men in Sudan, Ethiopia and southern Africa are the closest lineal descendants to the first Homo sapiens who left Africa New Guinea and Australia were settled early in the process New Guinea and Australia were settled early in the process Japan has remained in genetic isolation. Mutations are strikingly different from those of surrounding populations, they account by themselves as a specific haplogroup Japan has remained in genetic isolation. Mutations are strikingly different from those of surrounding populations, they account by themselves as a specific haplogroup Native Americans have a common ancestry with Eurasians and East Asians Native Americans have a common ancestry with Eurasians and East Asians

What did they find? In the tree obtained, the deepest root separated Africans from non-Africans. In the tree obtained, the deepest root separated Africans from non-Africans. Their calculations suggest the split happened an en estimated 115,000 to 156,000 years ago. Their calculations suggest the split happened an en estimated 115,000 to 156,000 years ago.

Fossils Archeologists find a fossil in Herto, Ethiopia dating about 160,000 years old Archeologists find a fossil in Herto, Ethiopia dating about 160,000 years old The oldest fossil found of Homo sapiens dates back 115,000, and is found in Israel. The oldest fossil found of Homo sapiens dates back 115,000, and is found in Israel. Researches link the fossil found in Israel to the fossil in Herto, Ethiopia and other fossils found in Africa, based on physical characteristics of the skull. Researches link the fossil found in Israel to the fossil in Herto, Ethiopia and other fossils found in Africa, based on physical characteristics of the skull.

Tools of Homo-erectus and Homo-Sapiens The Acheulean tool around 1.5 million years ago in East Central Africa. Homo ergaster and western Homo erectus. (1) chipping the stone from both sides to produce a symmetrical (bifacial) edge, (2) the shaping of an stone into a recognizable and repeated tool form, and (3) variation in the tool forms for different tool uses. The Upper Paleolithic from 40,000 to 12,000 years ago, originated independently in both Asia and (as early as 90,000 years ago) in Africa. shows a remarkable proliferation of tool forms, tool materials, and much greater complexity of toolmaking techniques. It also quickly diversified into distinctive regional styles,

Results A tree rooted in Africa A tree rooted in Africa Tree suggests that some Africans are closer to Europeans and Asians than to other Africans. Tree suggests that some Africans are closer to Europeans and Asians than to other Africans.

Conclusion DNA sequencing and fossil evidence shows that modern humans originated in Africa and migrated north out of African, then eventually to the rest of the world. DNA sequencing and fossil evidence shows that modern humans originated in Africa and migrated north out of African, then eventually to the rest of the world. Oldest fossils of modern humans are found in Africa dating around 160,000 years old. Oldest fossils of modern humans are found in Africa dating around 160,000 years old.