EXAM III: Human evolution

what animal shares a similar ancestor to humans?

, humans and apes have shared ancestry for all but the last few million years.

which migration gave rise to modern Homo sapiens ?.

,The Multiregional Hypothesis the great genetic similarity of all modern people is the product of occasional interbreeding between neighboring populations. hypothesis, the "Out of Africa" or replacement hypothesis, argues that all Homo sapiens throughout the world evolved from a second major migration out of Africa that occurred about 100,000 years ago. This migration completely replaced all the regional populations of Homo derived from the first hominid migrations.

what is the compromise between the replacement and multiregional hypotheses

--A compromise alternative to these extremes suggests that Homo sapiens originated and then dispersed from Africa 100,000 years ago. --These individuals then interbred with the regional descendents of the earlier H. erectus migration. --This hypothesis predicts that the genomes of indigenous people from around the world today should reflect a complex mix of ancestries.

Describe Lucy - A. afarensis

--A. afarensis had a brain the size of a chimpanzee, a prognathic jaw, longer arms (for some level of arboreal locomotion), and sexual dimorphism more apelike than human. --However, the pelvis and skull bones and fossiltracks showed that A. afarensis walked bipedally.

what chromosomal evidence is used to help find make a connection between ancestors?

--Comparisons of Y chromosomes in 2001 provide perhaps the most important genetic data so far. --The Y chromosome is passed from male to male through the generations of a family with a minimum of crossing over with the X chromosome. --The diversity among Y chromosomes is limited to mutations. --By comparing the Y chromosomes of males from various geographic regions, researchers were able to infer divergence from a common African ancestor less than 100,000 years ago.

what are some key changes in the family structure that happened during human evolution?

--In contrast to most ape species, monogamy, with long-term pair-bonding between mates, prevails in most human cultures. --Newborn humans infants are exceptionally dependent on their mothers, and the duration of parental care (and opportunities for enhanced learning) is much longer in humans than in other hominoids.

how is brain growth different for nonprimates and primates?

--Nonprimate mammals - The brain grows rapidly, while they are fetuses, but growth slows and stops soon after birth. --Primates - the brain (and skull) continues to grow after birth and the period is longer for a human than other primates.

how does mdna evidence differ for neanderthals?

--The mtDNA extracted from Neanderthal bones fall completely outside the range of mtDNA for modern Europeans. =--These data suggest that Neanderthals contributed nothing to the ancestry of anatomically modern humans in Europe

how does dna evidence help the replacement hypothesis?

--Using changes in mitochondrial DNA (mtDNA) among human populations as a molecular clock, research have reported a time of genetic divergence of about 100,000 years ago. --This is supported by genetic markers found in nuclear DNA.

what is the Mitochondrial Eve Theory

--mDNA is inherited completely from your mother. --Using mDNA, researchers claim to have traced all modern human groups back to an African ancestry of about 100,000 years ago.

Human evolution is marked by the evolution of what features?

-Brain Size. brain size in hominoids tripled over the past 6 million years. -Jaw Shape. Our hominoid ancestors had longer jaws - prognathic jaws - than those of modern humans. This resulted in a flatter face with more pronounced chins. -There were also changes in dentition (teeth). -Bipedal Posture. Based on fossil skeletons, it is clear that our hominoid ancestors walked on all four limbs when on the ground, like modern apes. The evolution of bipedal posture - upright posture and two-legged walking - is associated with key skeletal modifications seen in early hominid fossils. ---Reduced Size Differences Between the Sexes. In hominoids, a size difference between females and males is a major feature of sexual dimorphism. As humans evolved, the size differences decreased.

which of the australopithecines were evolutionary dead ends and which were either on, or close to, the phylogenetic lineage that led to the Homo branch?

-Two lineages appeared after A. afarensis: the larger"robust" australopithecines and the smaller,"gracile" australopithecines. -Most researchers agree that the robust australopithecines were an evolutionary dead end, and that the ancestors of Homo were among the gracile australopithecines.

what are the three stages of cultural evolution?

1. About 2 million years ago - Nomads of the African grasslands made tools, organized communal activities and divided labors. 2. About 10,000 - 15,000 years ago - The development of agriculture in Africa, Eurasia, and the Americas encouraged permanent settlements. 3. The Industrial Revolution began in the 18th century. Since then, new technology and the human population have escalated exponentially.

what evidence is their to indicate that our large brains evolved? how long ago did this happen?

A remarkably complete fossil of a young hominid known as "Turkana Boy" indicates that even larger brains had evolved by 1.6 million years ago.

what is under the genus australopithecus?

A. africanus, was discovered in 1924 by Raymond Dart in a quarry in South Africa. A. africanus probably walked fully erect and had humanlike hands and teeth. However, the brain was only about one-third the size of a modern human's brain. Various species of Australopithecus began appearing about 4.4 million years ago and existed for over 3.0 million years.

what is specific to the replacement hypothesis?

According to the replacement hypothesis, all of the world's populations diverged from anatomically modern Homo sapiens that evolved from an African H. erectus population and then migrated throughout the world about 100,000 years ago.

where did humans evolve?

All known hominid (human) fossils older than about 1.5 million years are from eastern and southern Africa.

desrcibe homo erectus:

Compared to H. habilis, H. erectus was taller, had a larger brain (averaging about 1,100 cm3), and had about the same level of sexual dimorphism as modern humans.

what are the effect of cultural evolution?

Cultural evolution outpaces biological evolution and we may be changing the world faster than many species can adapt. The rate of extinctions this century is 50 times greater than the average for the past 100,000 years. The overwhelming rate of extinction is due primarily to habitat destruction and chemical pollution, both functions of human cultural changes and overpopulation.

when was enlargement of the human brain first seen? what evidence is there of this?

Enlargement of the human brain is first evident in fossils dating to about 2.5 million years ago. Simple stone tools have been found at times with the larger-brained fossils. It is clear from the fossil record that after walking upright for more than two million years, hominids began to use their brains and hands to fashion tools.

what two things helped with cultural evolution?

Erect stance was a very radical anatomical change in our evolution and required major changes in the foot, pelvis and vertebral column. Enlargement of the brain was a secondary alteration made possible by prolonging the growth period of the skull and its contents.

what aided in cultural evolution? what has cultural evolution done for the human species?

Evolution of the human brain may have been anatomically simpler than acquiring an upright stance, but the consequences of cerebral growth have been enormous. Cultural evolution resulted in Homo sapiens becoming a species that could change the environment to meet its needs and not have to adapt to an environment through natural selection.

What is a hominid?

Hominid has a narrow meaning, and includes modern humans and their closest ancestors.

What is a homioid?

Hominoid is a term referring to great apes and humans collectively

what is the name of the first hominid species to migrate out of africa? what did they do once the migrated out?

Homo erectus was the first hominid species to migrate out of Africa, colonizing Asia and Europe.

who was part of the large speciation event among African mammals?

Homo habilis and other new hominids were a part of a larger speciation event among African mammals, about 2.5 million years ago, as Africa's climate began to become drier and savannas started to replace forests.

who did homo habilis coexist with?

Homo habilis coexisted with the smaller-brained Australopithecus for nearly one million years.

what is the earliest fossils that anthropologists placed in our genus? What are they classified as?

Homo habilis. ("Handy man") Sharp stone tools found with these fossils, indicate that some hominids had started to use their brains and hands to fashion tools.

what animal is the closest living relative of man? What percentage of our DNA is identical?

However, chimpanzees are the closest living relatives of man ( Our DNA is > 90% identical )

Humans are the ______________of large animals.

Humans are the most numerous and widespread of large animals.

who is lucy a. afarensis?

In 1974, a new fossil, about 40% complete, was discovered in the Afar region of Ethiopia by Don Johansen. This fossil, nicknamed "Lucy," was described as a new species, A. afarensis. Lucy is estimated to be about 3.2 million years old.

What is Laetoli?

Laetoli is a place where they found fossil track of a family group of hominids that walked upright.

how was learning culture passed on?

Learning from the experiences of earlier generations is the basis of culture (transmission of accumulated knowledge over generations); the transmission is by written and spoken language.

What are some misconceptions of human evolution? Why is this misconception wrong?

Misconception - Humans are descended from chimpanzees Chimpanzees and humans represent two divergent branches of the hominoid tree that evolved from a common ancestor that was neither a chimpanzee nor a human.

describe Neanderthals. who are they descendants of?

Neanderthals had brains as large as ours, though somewhat different in shape. Neanderthals were generally more heavily built than modern humans. Neanderthals are descendants of Homo erectus, but are not believed to be ancestors of modern humans.

In Europe, H. erectus gave rise to the humans known as ______________

Neanderthals.

are humans still evolving?

No significant biological change in humans has occurred from the beginning to now, however, humans are still evolving.

what hypothesis came about both Australopithecus and Homo habilis ?

One hypothesis is that Australopithecus was an evolutionary dead end, while Homo habilis led to Homo erectus which later gave rise to Homo sapiens.

what is paleoanthropology?

Paleoanthropology is the study of human origins and evolution. It focuses on the tiny fraction of geologic time during which humans and chimpanzees diverged from a common ancestor

What evidence supports the replacement hypothesis?

So far, the genetic data have mostly supported the replacement hypothesis.

what major evolutionary changes occurred as modern humans began to evolve?

Some of the major evolutionary changes leading to our species may have occurred as our ancestors came to live less in the trees and spent more time walking on the ground in more open habitats.

what kind of ancestor did humans and chimpanzees come from? What evidence proves this?

The fossil record and comparisons of DNA between human and chimpanzees indicate that they diverged from a common hominoid ancestor only about 5 - 7 million years ago

what information is specific to the multiregional hypothesis?

The multiregional hypothesis places that last common ancestor in Africa over 1.5 million years ago, when H. erectus began migrating to other parts of the world .

what is the name of the oldest fossil that is more human than ape?

The oldest fossil that is unambiguously more human than ape is Australopithecus anamensis, which lived over 4 million years ago and walked upright.

what are australopithecus?

The various pre-Homo hominids are classified in the genus Australopithecus.

what does western european fossil evidence indicate?

The western European fossil evidence indicates the total replacement of Neanderthals about 40,000 years ago by anatomically modern humans, known as Cro-Magnons. There were no intermediates suggesting interbreeding between Neanderthals and the later arrivals.

What are the names of the two hominid group?

There are two main groups of hominids: the australopithecines, which came first and are all extinct members of the genus Homo, with all species extinct except one: Homo sapiens.

what did Homo habilis look like?

This species had less prognathic jaws and larger brains than australopithecines.

what does fossil evidence from outside Europe indicate?

fossil evidence from outside Europe is more ambiguous. Some Asian fossils may show intermediates between older fossils of H. erectus and the skeletal features of modern Asians.

What kind of features did hominids have for two million years?

hominids walked upright for two million years without a substantial increase in brain size. This may have freed the hands for other things such as gathering food or caring for infants.

What is a human evolution myth?

human evolution generated during the early part of the twentieth century that

what is the timeline of hominid fossils?

is Australopithecus anamensis, which lived over 4 million years ago and walked upright. Other fossils of putative hominids go back 6 million years, closer to the ape-human split that molecular systematists estimate occurred about 5 - 7 million years ago.

What is the name of thee type of evolution humans went through?

mosaic evolution, Different features evolved at different rates,

are all regional descendants of h. erectus dead ends?

yes

are there any hominid species that predate a. afrensis?

yes, Australopithecus anamensis