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  TOPIC:  human evolution

HUMAN EVOLUTION

INTRODUCTION

 

Human evolution is the lengthily process of change by which people originated from apelike ancestors scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved ever a period of approximately six million years ago.

One of the earliest defining human traits, vipedalism—the ability to walk on two legs—evolved over 4 million years ago. Other important human characteristics –such as large and complex brain, the ability to make and use tools. And the capacity for language---developed more recently. Many advanced traits –including complex symbol expression, art and elaborate cultural diversity—emerged mainly during the past, 100,000 years.

Humans are primates. Physical and genetic similarities show that the modern human species,Homo sapiens, has a very close relationship to another group of primate species, the apes. Humans and the great apes(Large apes) of Africa---chimpanzees(including booboos, or so called “pygmy chimpanzees”) and gorillas—share a common ancestor that lived between 8 and 6 million years ago.

Humans first evolved in Africa and much of human evolution occurred on that continent. The fossils of early humans who lived between 6 and 2 million tears ago come entirely from Africa.

Mist scientists currently recognize some 15 to 20 different species of early humans. Scientists do not all agree, however, about how these species are related or which ones simply died out. Many early human species—certainly the majority of them- left no living descendants. Scientists also debate over how to identify and classify particular species ode ally humans, and about what factors influenced the evolution and extinction of each species.

Early humans first migrated out of Africa into Asia probably between 2 million and 1.8 million years ago. They entered Europe somewhat later, between 1.50millon to 1 million years ago. Species of modern humans populated many parts of the world much later. For instance people came to Australia probably within the past 60,000 years and to the Americans within the past 30,000 years or so .The beginnings of agriculture and the rise of the first civilizations occurred within the past 12,000 years.

 

Pale Anthropology:

 

“Pale anthropology is the scientific study of human evolution.

Pale anthropology is a subfield of anthropology, the study of human culture, society and biology. The field involves an understanding of the similarities and differenced between humans and other species in their genes, body form physiology, and behavior.”

 

 

 

 

 

 

 

 

 

ORIGIN

Our evolutionary history is written into our genome.

The Human genome looks the way it does because of all the genetic changes that have affected our ancestors. The exact origin of modern humans has long been a topic of debate.

Modern humans (Homo sapiens), the species that we are, mean ‘wise man’ in Latin. Our species is the only surviving species of the genus Homo but where we came from has been a topic of much debate. Modern humans originated in Africa within the past 200,000 years and evolved from their most likely recent common ancestors, Homo erectus which means upright man in “Latin” Homo erectus is an extinct species of human they lived between 1.9 million and 135,000 years ago.

Historically, two key models have been put forward to explain the evolution of Homo sapiens. These are the ‘out of Africa model and the ‘molto regional ‘model. The ‘out of Africa’ model is currently the most widely accepted model. It proposes that Homo sapiens evolved in Africa before migrating across the world.

On the other hand the ‘multi-regional’ model proposes that the evolution of Homo sapiens took place in a number of places over a long period of time. The intermingling of the various populations eventually led to the single Homo sapiens species we see today.

This is still very much an area of active research , however, current genomic evidence supports a single  ‘out of Africa’ migration of modern humans rather than the ‘ multi-regional’model.Although, studies of the genomes of the extinct hominids Neanderthals and Denis vans suggest that there was  some mixing of genome with humans in Europe and Asia. This interbreeding between two previously separated populations is called’ admixture’ and results in a mixing of genes between the populations.

 

STAGES  OF  HUMAN  EVOLUTION

MAINLY CONSISTS OF THREE STAGES;

[A] APE FOSSILS

[B] PRE-HISTORIC MAN

[C]MODERN MAN

 

[A] APE FOSSILS:

1.Dryopithecus and Ramapithecus-

Ø About 15 Mya, primates called Dryopithecus and Rematches were existing.

Ø They were hairy and walked like gorillas and chimpanzees.

Ø Ramapithecus was more man like while Dryopithecus was more ape like.

Ø
Few fossils of man like bones have been discovered in Ethiopia and Tanzania.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.SHIVAPAITHECUS-

Fossils discovered from Shivalik Hills in India.

 

3.KENYAPITHECUS-

Fossils discovered from Kenya.

 

4.AUSTRALOPITHECUS-

They lived in East African Grassland. According to the evidence , they hunted with stone weapons but essentially ate fruit. It is considered connecting link between apes and man.

Ape like characters:

·      Less cranial capacity

·      Thick hair growth

·      U shaped jaw

·      Larger and sharper teeth

Man like characters:

·      Erect posture and bipedal locomotion

·      Forelimbs shorter than hind limbs

·      Vertebral column with distinct lumber curve

 

 

[b] pre –historic man:

 

1.Homo Habilis:

·      The brain capacities were between 650-800cc.

·      They probably did not eat meat.

·      They were the makers of stone tools.

This species, one of the earliest members of the genus Homo, has a slightly larger braincase and smaller face and teeth than in Australopithecus or older hominine species. But it still retains some ape-like features, including ling arms and a moderately-pragmatic face its name, which means ‘handy man’, was given in 1964 because this species was thought to represent the first maker of stone tools. Currently, the oldest tools are dared slightly older than the oldest evidence of the genus Homo.

 

2.Homo Erectus:

·      About 1.5 may, Homo erectus arose.

·      Homo erectus had a large brain around 900cc.

·      Homo erectus probably ate meat.

Early African Homo rectus fossils are the oldest known early humans to have possessed modern human-like body proportions with relatively elongated legs and shorter arms compared to the size of the torso. These features are considered adaptations to alive lived on the ground. Compared with earlier fossil humans, note the expanded braincase relative to the size of the face. The most complete fossil individual of this species is known as the ‘Turkana Boy’- a well preserved skeleton , dated around 1.6 million years ago. The appearance of Homo erectus in the fossil recorded is often associated with the earliest handles, the first major innovation in stone tool technology.

Early fossil discoveries from Java and China comprise the classic example of this species. Generally considered to have been the first species to have expanded beyond Africa, Homo erectus is considered a highly variable species pared over two continents the longest lived early human species- about nine times as long as our own species, Homo sapiens, has been around!

 

Also includes:

a)  Java Man-Homo erectus

·      Fossils found in 1891

·      Omnivorous

·      Cranial capacity-800 to 1000cc

·      1^st man who used fire

b)   Packing Man – Homo erectus pokiness

·      W.C  Pei discovered fossils from China

·      They used fire for cooking meat and protection

·      Cranial capacity—850 to 1300 cc

·      They were omnivorous

c)   Heidelberg Man—

·      First fossils recovered from Heidelberg in Germany.

·      This man had evolved as a branch from main line of evolution but soon go extinct.

 

3. Homo sapiens:

Homo erectus were succeeded by early Homo sapiens, which were decreased under different names neanderthalensis, Homo heildelbergensis etc. But, since they are grouped under Homo sapiens

 

Subspecies of Homo sapiens are:

 

a)  Neanderthal Man- Homo sapiens neanderthalensis

·     They were lived near East and central Asia between 100,000 to 40,000 years back.

·     Fossils was discovered by Fulhrott in Neanderthal valley of Germany.

·     Cranial capacity_1400cc

·     They used hides to protect their bodies made with skin of animals.

·     They buried their dead and believed in immortality of souls.

·     They lived in huts.

·     Omnivorous in nature.

·     Development of speech and language started at this stage.

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b) Cro-Magnon Manhood sapiens fossil’s

 

·     Origin and evolution 50,000 to 10,000 yr ago.

·     Fossils discovered by Mac. Gregory from Cro-Magnon rocks of France

·     Cranial capacity 1650cc

·     They lived in caves

·     Omnivorous

·     They had large forehead and well developed chin

·     Semi circular Jaw and orthoganathus face

·     Speech and language were developed in them

·     They wore clothes of animal skin

·     Domestication was started by this man

·     They also painted beautiful paintings on cave wall

·     Hence pre historic cave art started 18000 years ago

 

 

[C] MODERN MAN:

 

Homo sapiens:

·      During ice age between 75000 to 10000 yr ago modern homo sapiens arose

·      It arose in Africa and moved across continents and developed into distinct races

·      This is the man today having the brain capacity of 13000 to 1600cc

·      This man has well developed chin wall developed speech centre , smaller forehead and reduced body hair.

·      Semi circular jaw and orthognathous face

·      It is omnivorous by nature

·      Agriculture was also started by this man 10000 yr back

·      Human settlements started.

 

 

 

 

 

 

 

 

CONCLUSION

The rate of evolution for our species has continuously accelerated since the end of last ice age, roughly 10,000 yr ago.

For instance, our larger and denser populations have made it far easier for contagious diseases, such as tuberculosis, small pox the plague, and influenza to rapidly spread through communities and wreak havoc. This has exerted strong selection for individuals who were fortunate to have immune system that allowed them to survive. This is mostly due to have fact that our human population had explosively grown and moved into new kinds of environments including cities , where we have been subject to new natural selection pressures. There also has been a marked change in diet for most people since the end of the last ice age. It is now less varied predominantly vegetarian around the globe with a heavy dependence on foods made from cereal grains. It is likely that  human species has been able to adapt to these and other new environmental pressure bra cause it has acquired a steadily greater genetic diversity. A larger populations naturally has more mutations adding variations to its  gene pool simply because there are more people.

This happens even if the mutation rate per person remains the same. However the mutating rate may have been exposed to new kinds of man- made environmental pollution that can cause additional mutations. It is not clear what all of the consequences of the environmental and behavioural changes for humans have been. However it does appear that average human body size has become somewhat shorter over the last 10000 years. and we have acquired widespread immunity  to the more severe effects of some diseases such as measles and influenza. It remains to be seen how we will use this technology in the future and whether we will continue as a specie, evolve into another species, or become extinct as many groups have before us.

 

                      MADE BY: ANUJ VASHISHTHA……….

                       CLASS:       B.SC 2nd year(3rd semester)

              COLLEGE :Swami Vivekananda mahavidhyalya