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Human
Temporal range: Pleistocene
Man and Woman
Scientific classification
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Binomial name
Homo sapiens
Trinomial name
Homo sapiens sapiens
Linnaeus, 1758

Human evolution is the biological and cultural evolution of the subspecies homo sapiens sapiens, or human beings.

Research[edit]

There are three main areas that encompass the study of human evolution, primatology, paleontology and paleoanthropology.

Primatology is the branch of zoology that deals with the study of evolutionary biology and behaviour of non-human primates. Modern primatology is an extremely diverse science, which ranges from anatomical studies of primate ancestors and field studies of primates in their natural habitat, to experiments in animal psychology and great ape language. It has cast an immense amount of light on basic human behavioral ecology and the ancient ancestry of these behaviours.

Paleontology is the science of the forms of life existing in former geologic periods, as represented by their fossils. Paleontologists search for the origin of human nature including the evolution of human biology, human anatomy, human physical appearance, human behavior, evolutionary psychology and human genetics.

Paleoanthropology is the branch of biological anthropology that researches the fossil record of hominids and studies the mechanisms of biological evolution, biological inheritance, adaptation, genetic variation and comparative anatomy.

Evolution[edit]

Evolutionary biology is change in the heritable traits of a population over successive generations, as determined by shifts in the allele frequencies of genes.[1] Over time, this process can result in speciation, the development of new species from existing ones. All contemporary organisms on earth are related to each other through common descent, the products of cumulative evolutionary changes over billions of years. Evolution is thus the source of the vast diversity of life on Earth, including the many extinct species attested to in the fossil record.[2][3]

The history of evolutionary thought has been around since ancient times. Modern evolutionism is based on the theory of natural selection,[4] which was first set out in a joint 1858 paper by Charles Darwin and Alfred Russel Wallace and popularized in Darwin's 1859 book The Origin of Species. In the 1930s, Darwinian natural selection was combined with the theory of Mendelian heredity to form the modern evolutionary synthesis, also known as "Neo-Darwinism". The modern synthesis describes evolution as a change in the frequency of alleles within a population from one generation to the next. With its enormous explanatory and predictive power, this theory has become the central organizing principle of modern biology, relating directly to topics such as the origin of antibiotic resistance in bacteria, eusociality in insects, and the staggering biodiversity of Earth's ecosystem. This lead to population genetics, which is the study of the allele frequency distribution and change under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and gene flow.

Thomas Henry Huxley 1863

Evolution in organisms took place over thousands and millions of years, making direct observation impossible. In the 1600s scientists realized that sedimentary rock contained remains of organisms and the sedimentary layers could be used as a type of calender to date them. These fossil records provide evidence for evolution.

Evolutionary thought has produced other evidence of evolution beyond the fossil record.

Descent with modification first coined by Charles Darwin, provides important evidence how animals might be related to one another and how they evolved. For example, comparative anatomy sometimes appear in the human embryo with the early states of development showing tails and gill arches. These brief developments reflect common descent from an ancient ancestor and heredity by all descendants.

Vestigial structures are anatomical structures of organisms in a species, which are considered to have lost much or all of their original function through evolution. These structures are typically in a degenerate, atrophied, or rudimentary condition or form. The human appendix is a vestigial structure, useful for digestion in animals that eat mostly plants, which was important to our distant ancestors, with no use to modern humans.

Proteomics is the large-scale study of protein, particularly their structures and functions. This term was coined to make an analogy with genomics and while it is often viewed as the "next step", proteomics is much more complicated than genomics. Biologists compared the 104 amino acid sequence in human Cytochrome c and determined it is identical to Chimpanzees.

Biogeography is the range different species are distributed throughout the world, which provides evidence of evolution. The Mitochondrial Eve is the name given by researchers to the woman who is the matrilineal most recent common ancestor for all living humans; the mitochondrial DNA (mtDNA) in all living humans is derived from hers. Mitochondrial Eve is the female counterpart of the Y-chromosomal Adam, the patrilineal most recent common ancestor. The holder of this title is believed by some to have lived about 150,000 years ago in what is now Ethiopia, Kenya or Tanzania and all human migration began from that point. The time she lived is calculated based on the molecular clock technique of correlating elapsed time with observed genetic drift.

Opposition[edit]

Some people do not support evolution as it conflicts with their religous beliefs of creationism. The creation-evolution controversy is a recurring dispute about the origins of the Earth, humanity and the origin of life. Another opposing belief is intelligent design, which is the concept that certain features of the universe and of living things are best explained by an intelligent designer, not an undirected process such as natural selection. The intelligent design movement is a neo-creationist campaign that arose out of Christian fundamentalism and an evangelistic creation science movement in the United States that calls for broad social, academic and political change.[5][6][7]

In contrast, theistic evolution is a view about how the science of evolution relates to some religious interpretations. More specifically, it is the general opinion that some or all classical religious teachings about God and creation are compatible with some or all of the human understanding about biological evolution.

Phylogenetic tree[edit]

Phylogenetics is the study of evolutionary relatedness among various groups of organisms. The phylogenetic tree shows the cladistic interrelationships among various species that have a common ancestor.[8] Scientific classification is how biologists group and categorize extinct and living species of organisms and belongs to the science of taxonomy or biological systematics. Molecular systematics, which uses DNA sequences as data, has driven many recent revisions in classification. This system can be used to reflect how our own subspecies of human fits into the tree.

The superkingdom taxon is at the base of the tree. In the three-superkingdom system the eukaryote is an organism with a complex cell or cells in which the genetic material is organized into a membrane-bound nucleus and comprise animals, plants, and fungi.

The kingdom is the next taxon and humans are a member of the animals.

Traditionally, animals have been divided into two subphylum with humans belonging to the vertebrates. The first vertebrates were fish that lived 400 MYA. The legacy of some fish anatomy from these distant aquatic ancestors remains with humans including a vertebral column flanked by pairs of muscles. Evolving from salt water fish has caused the hemolymph to be composed of salty water to fill all of the interior hemocoel of the human anatomy and it surrounds all cells. We have a sensory system and enclosed brain typical of a vertebrate. The characteristic tail found in most verterbrates appears and disappears during the blastocyst embryo stage of humans. The gill slits appear only fleetingly in the blastocyst stage, with one evolved into the eustachian tube.

There are five classes of vertebrates and humans are a mammal. Approximately twenty-one orders of mammals exist, with humans a member of the primates.

Primate[edit]

The order Primate is comprised of two suborders, strepsirrhini and haplorrhini. The suborder haplorrhini breaks down into the infraorder simiiformes and the parvorder catarrhini.

The majority of primates are tree-dwellers living in jungles between the tropics. We share many primate features, including but not limited to, hands, face, binocular vision and colour vision, typical vestiges of tree climbing ancestors. Primate social organisation and behaviour are complex, where survival depends on navigating a web of social interactions, similiar to humans.[9]

The superfamily hominoidea and the family hominidae, includes chimpanzees, gorillas, orangutans and humans.[10]

Extant Hominoid family tree

It is common knowledge that humans share about 98.5% of their genes with chimpanzees, who are humans closest living relatives. However, humans did not evolve from chimps, but rather we shared a common ancestor species of ape. The subfamily homininae includes humans and some extinct relatives, gorillas and chimpanzees. It comprises all those hominids, such as australopithecus, that arose after the split from the other great apes, of which orangutans are the only surviving group. Hominini is the tribe of homininae that only includes humans (Homo), chimpanzees (Pan), and their extinct ancestors. Members of this tribe are called hominins.[11]

The more anthropomorphic primates are placed in the subtribe hominina, which are characterized by a progression of increasingly erect bipedal locomotion. The only existing species is homo sapiens. Fossil records indicate this subtribe branched from our most common living ancestor the chimpanzee about 3 to 5 MYA. This subtribe is usually described to include australopithecus, paranthropus, sahelanthropus, orrorin, ardipithecus and homo. However, the exact makeup is still under debate, as some scientists struggle to determine the order of descent in human evolution.

Pre-Homo[edit]

Eight MYA the African arboreal savanna was altered due to climate change, causing the spaces between trees to increase forcing quadruped prehistoric apes to travel greater distances on the ground and through long grass, which impaired their ability to sight landmarks or approaching predators. To compensate ape's began to display intermittent bipedal upright locomotion, allowing them to know their location and any necessary directional change. However, experts still remain divided on the exact development of bipedalism.[12]

Our anthropomorphic ancestors great bipedal innovation caused permanent changes in their skeleton. Over time their skulls attained a position at the top of the vertebral column and not on its forward-facing extension as in most mammals. This repositioning lead to a brain development in the rear portion of the skull. The erect posture neck muscles shrank, relaxing their hold on the skull. The spine attained a distinct curvature and the pelvis became more vertical. Standing upright pre-homos used their hands for all sorts of tasks besides grasping.

Sahelanthropus[edit]

The genus sahelanthropus has but one known species sahelanthropus tchadensis, which is dated 7 MYA and is the oldest known pre-homo to date.[13] The remains discovered were nicknamed "Toumai" meaning "Hope of Life" in the Dazaga language and were found in Chad, which proves that this species occupied a much wider territory than experts previously thought.[14] Toumai displays pre-homo characteristics comprising a relatively flat face and an occipital opening confirming bipedal locomotion. The small brain capacity some 350cm³ (21in³) is approximately the same size as a chimpanzee brain.[15] Toumai is believed to represent the period immediately subsequent to the separation of chimpanzee and hominind. This species might be related to the group that produced, one million years later, the next link in the chain called Orrorin.

Orrorin[edit]

The genus orrorin contains one known species orrorin tugenensis, which lived during the miocene period some 6 MYA.[16] In the Tugen language, orrorin means 'earliest man' and 'tugenensis' refers to the Tugen Hills where the remains were found.[17] This species exhibits a femur, joint size and gluteal muscles that offer compelling evidence that it was bipedal and stood 1.5m (5ft) and weighed between 30 and 40kg (66 to 88lbs). The teeth display chimpanzee-like features, but the tooth enamel thickness is closer to that found on modern human teeth.

Ardipithecus[edit]

The genus ardipithecus comes from the Greek word 'Afar' meaning 'Ground Ape'. This genus has two known species ardipithecus kadabba and ardipithecus ramidus, which lived in the region of Ethiopia[18] between 4.4 and 6 MYA. The fossil remains are incomplete and fragmentary, but in general, this genus displays characteristics of both the ape and australopithecine.[19][20]

Australopithecus[edit]

Homo[edit]

Origin and migration[edit]

  1. Single origin theory - Out of Africa
  2. Multiple origin theory
  3. Combined theories

Subsistence[edit]

  1. Food
  2. Hunting
  3. etc.

Tools[edit]

Fire[edit]

Adaptation[edit]

Symbolic thought[edit]

Language[edit]

Art[edit]

Music[edit]

Religion[edit]

See a larger version.

Oldest known religious artifact found Botswana "snake rock" may show Stone Age religion

Science[edit]

Agriculture[edit]

Civilization[edit]

  1. Urban

Society[edit]

Culture[edit]

  1. Sociocultural evolution

Gerhard Lenski, a sociologist, differentiates societies based on their level of technology, communication and economy: (1) hunters and gatherers, (2) simple agricultural, (3) advanced agricultural, (4) industrial.[21] This is somewhat similar to the system earlier developed by anthropologists Morton H. Fried, a conflict theorist, and Elman Service, an integration theorist, who have produced a system of classification for societies in all human cultures based on the evolution of social inequality and the role of the state. This system of classification contains four categories:

Over time, some cultures have progressed toward more-complex forms of organization and control. This cultural evolution has a profound effect on patterns of community. Hunter-gatherer tribes settled around seasonal foodstocks to become agrarian villages. Villages grew to become towns and cities. Cities turned into city-states and nation-states.[22]


4

Hominin Species Distributed Through Time edit
Homo (genus)AustralopithecusArdipithecusParanthropusParanthropus robustusParanthropus boiseiParanthropus aethiopicusHomo sapiensHomo neanderthalensisHomo heidelbergensisHomo erectusHomo floresiensisHomo georgicusHomo habilisAustralopithecus garhiAustralopithecus africanusAustralopithecus bahrelghazaliAustralopithecus afarensisAustralopithecus anamensisOrrorin tugenensisSahelanthropus tchadensisPleistocenePlioceneMiocene

Comparative table of Homo species[edit]

species lived when (MYA) lived where adult length (m) adult weight (kg) brain volume (cm³) fossil record discovery / publication of name
H. habilis 2.5–1.5 Africa 1.0–1.5 30–55 600 many 1960/1964
H. rudolfensis 1.9 Kenya       1 skull 1972/1986
H. georgicus 1.8–1.6 Georgia     600 few 1999/2002
H. ergaster 1.9–1.25 E. and S. Africa 1.9   700–850 many 1975
H. erectus 2(1.25)–0.3 Africa, Eurasia (Java, China, Caucasus) 1.8 60 900–1100 many 1891/1892
H. cepranensis 0.8? Italy       1 skull cap 1994/2003
H. antecessor 0.8–0.35 Spain, England 1.75 90 1000 3 sites 1997
H. heidelbergensis 0.6–0.25 Europe, Africa, China 1.8 60 1100–1400 many 1908
H. neanderthalensis 0.23–0.03 Europe, W. Asia 1.6 55–70 (heavily built) 1200-1700 many (1829)/1864
H. rhodesiensis 0.3–0.12 Zambia     1300 very few 1921
H. sapiens 0.25–present worldwide 1.4–1.9 55–80 1000–1850 still living —/1758
H. sapiens idaltu 0.16 Ethiopia     1450 3 craniums 1997/2003
H. floresiensis 0.10–0.012 Indonesia 1.0 25 400 7 individuals 2003/2004

References[edit]

  1. ^ Talk Origins - Introduction to Evolutionary Biology
  2. ^ Futuyma, Douglas J. (2005). Evolution. Sunderland, Massachusetts: Sinauer Associates, Inc. ISBN 0-87893-187-2.
  3. ^ Gould, Stephen J. (2002). The Structure of Evolutionary Theory. Belknap Press. ISBN 0-674-00613-5.
  4. ^ W.W. Norton - Adaptation by Natural Selection
  5. ^ The Evolutionary War
  6. ^ Talk Origins - What is Creationism?
  7. ^ National Center for Science Education
  8. ^ Tree of Life web project
  9. ^ W.W. Norton - The Evolution of Social Behavior
  10. ^ W.W. Norton - From Tree Shrew to Ape
  11. ^ Smithsonian - Humans as Primates
  12. ^ Smithsonian - Explaining Bipedalism
  13. ^ Sahelanthropus.com
  14. ^ Talk Origins - "Toumaï", Sahelanthropus tchadensis
  15. ^ Live Science - New Findings Bolster Case for Ancient Human Ancestor
  16. ^ UCLA - Orrorin Tugenensis
  17. ^ BBC: First chimpanzee fossils found
  18. ^ BBC: Amazing hominid haul in Ethiopia
  19. ^ Archaelogy Info - Ardipithecus ramidus
  20. ^ Minnesota State University - Ardipithecus ramidus
  21. ^ Lenski, G. 1974. Human Societies: An Introduction to Macrosociology.
  22. ^ Effland, R. 1998. The Cultural Evolution of Civilizations.

See also[edit]

External links[edit]

Category:Human evolution Category:Neogene

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