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|Taxonomy | Eukarya (more phylums) | Evolution | Phylogenetic Trees | Extinctions|
Evolution of Man (Much of this is theory which is continuing to evolve.)
Biologists have long aspired to paint a genetic portrait of the ancestor by running the tree of evolution backward, going from its leaves -- the living creatures of today -- down to the point where all its branches coalesce in a single trunk.
The rapid (geologically speaking!) diversification of the animals has made it difficult to establish the genealogical relationships between them.
Some reptiles changed so that they could be active even when it was cool. These were the warm blooded cynodonts. They may have had fur to help keep them warm. They could feed at night when other reptiles could not. A new mammal, the primate, appeared about 56 million years ago (mya). The monkeys evolved first and then the apes.
Most ideas and theory on animal evolution are based on:
ARCHAEA [Domain] Bacteria (single cell, no nucleus) 3bya Eukaryotes [Domain] Protozoa (Cells with a nucleus) 1.2 bya Animalia [Kingdom] Sponges [Phylum Porifera] (Grouping of cells in an organized colony) 0.8-1bya JellyFish (primative nervous system and muscles) 600 mya Coral Flataworms (Phylum Platyhelminthes) 600-1,000 mya (beginnings of a head - mouth and light sensitive spots) Brachiopods Mollusks [Phylum] Nautilus 550 mya Trilobites (High-definition eyes) Squid Echinoderms [Phylum] (star fish) 540 mya Lancet Family Alepisauridae (protofish) (Cephalochordata, Amphioxus 440 mya Chordata [Phylum] nerve chord. 570 mya Urochordata [Class] (Sea Squirts, Tunicates, Ascidians, etc.) Vertebrates [Sub-Phylum] 525 mya Agnathans are jawless fish. There are two primary marine types of the class Agnatha. They are Hagfish and Lampreys. 500 mya Bony Fish - 470 mya Fish 400 mya Coelacanth (Lungfish) 350 mya Tetrapods (terrestrial vertebrates - 4 appendages legs or legs+wings) 350 mya Amphibians Synapsida [Class]- (extinct) (looked like reptiles) (300 mya) Pelycosaurs ("mammal- looked like reptiles") 290 mya Therapsida [Order]- The dominant land animals during the Middle Permian. Cynodonts 222 - 215 mya Early Mammals [Class] (shrew like) 195-164 mya 85% genetically similar to humans Early primates [Order] (lemurs, monkeys, ...) 56 mya (Million years ago)Characterized by: Grasping hands, flexible arms, acute 3-D vision, learned behavior, urge for social connections.
93% genetically similar to humans. See DNA below.
Proconsul is an extinct genus of primate without a tail existed from 23 to 17 million years ago in eastern Africa. It is a likely candidate for a common ancestor to apes.
Hominoids [SuperFamily] Apes (Gibbons, ..) 25 mya
Hominidae [Family] Great Apes (Orangutans, ..) 15 mya
Homininae [Sub-Family] (Gorilla, man, chimp) 13 mya [semi-upright posture] 98.4% genetically similar to humans
A 13 million year old fossil discovered in 2004 in spain, Pierolapithecus catalaunicus, is a candidate for a common ancestor between apes and Hominini (chimps and humans). See Gorilla walks like a man YouTube
Hominini [Tribe (chimp, man) 7 mya
Sahelanthropus tchadensis 7 - 6 mya Orrorin tugenensis 6.2 - 5.8 mya Ardipithecus ramidus 4.4 mya [becoming bipedal] (see The Middle Awash project at Berkeley and Discovering Ardi at the discovery channel) Australopithecus [Genus] 4 - 2 mya Afarensis [Species] 3.9 - 3 mya (Lucy) [mostly bipedal] * Africanus 3.3 - 2.1 mya * Paranthropus Boisei 2.3 - 1.2 mya Robustus 1.8 - 1.2 mya Homo [Genus] 1-2 mya Probably evolved from Australopithecus Homo Habilis [Species] 2.4 - 1.4 mya * Homo Erectus [Species] 1.9 mya- 143,000 ya Archaic Homo Sapiens The term is typically taken to include several varieties of Homo. 500,000 - Including: Homo heidelbergensis 700,000 - 200,000 ya [large brain] * Homo neanderthalensis 200,000 - 28,000 ya and Homo rhodesiensis 300,000-125,000 ya Homo Sapien Sapien (Anatomically Modern Man) 120,000 - 200,000 ya - present Full behavioral modernity - 50,000 ya * Viable candidate for an ancestor of humans.
Classification: Taxonomy & Systematics
Human Family Timeline:|
Human Evolution Timeline @ The Smithsonian Institution's Human Origins Program
Human Family Tree at The Smithsonian
Chart of Human Evolution at handprint.
The Evolution of Homo sapiens by John W. Kimball, PhD.
Range of Great Apes 12 million years ago to 5 Million years ago.
The 1.8 million year old homo erectus fossil in Java and later homo erectus fossils in China indicates there was an early migration.
One theory was that homo sapiens evolved independently there and in Africa. The dominant view among scientists now is the "Out of Africa" or recent African origin hypothesis, which argues that Homo sapiens arose in Africa and migrated out of the continent around 50,000 to 100,000 years ago, replacing populations of Homo erectus in Asia and Homo neanderthalensis in Europe.
There are differing theories on whether there was a single exodus or several. A multiple dispersal model involves the Southern Dispersal theory. In this theory, there was a coastal dispersal of modern humans from the Horn of Africa around 70,000 years ago.
See Human Migration in History
Common view of human ancestors. This is still theory.
In 2008 a finger bone was found in the Denisova Cave in southern Siberia.
Genetic sequencing suggest that it contributed 4-6% of its genetic material to the genomes of present-day Melanesians (People from Melanesia [New Guinea, ...]). The phalanx was
found in a layer, which has been dated to 50,000 to 30,000 years ago. Speculation is it was a branch of Neanderthals which interbred with Homo Sapiens.
Is there a missing link? - A "missing link" implies a linear progression from one species to another. But evolution occurs in branching patterns, making a multibranched tree a more appropriate model for understanding evolutionary relationships.
Most of the Homanin fossils have been found in East Africa's Great Rift System (EARS) (A place where tectonic forces are presently trying to create new plates by splitting apart old ones.). However the earliest Homanin, Sahelanthropus tachadensis (Sahel Man from Chad) was found in Chad, north central Africa.
See: Hominidae in taxonomy.
bya - Billion Years ago
Sponges Graptolites - Extinct small marine animals related to Hemichordata Cnidarians - jellyfish, coral, sea anemones Moss Animals - Bryozoa look like coral or seaweed Brachiopods - lamp shells (clam like animals that live in extreme cold waters) Mollusks - oysters, snails, slugs, scallops, octopus, squid and clams Anthropods - Insects - butterflies, grasshoppers, beetles, fly, mosquito, moths Echinoderms - starfish, sea urchins Chordates - Vertibrates - fish, reptiles, birds, amphibians, mammalsThe width of the shaded space is an indicator of the number of species.
Source: The Modern View Of Evolution at Estrella Mountain Community College from Life: The Science of Biology, by Purves et al., from Sinauer Associates.
Life evolved very slowely until the cambrian explosion about 530 million years ago.
Origins of Life:
1953 - Miller-Urey Experiment
2001 To answer the question of which came first a cell membraned or genetic molecules, Szostak, Bartel and Luisi's paper "Synthesizing Life" (Nature. 2001; 409: 387-390) state that a protocell and genetic molecule had to develop in parallel.
Szostak at Mass. General has shown since how simple fatty acids around in the primative earth could form cell membranes.
2009 - Sutherland article in Nature
Cladistic trees, a system based on the a common evolutionary history to group "closely related organisms" has been accepted as the best method available for phylogenetic analysis since the early 2000's.
|Archaea was shown to be closer than bacteria to Eukayra (Protista, Animilia, Plante, Fungi) by comparing ribosomal RNA sequences. Carl Woese, 1977|
See: Phylogenetic trees
Clades for Humans:|
Links to Tree of Life Web (ToL) and Univ. of California Museum of Paleontology (UCMP):
The pufferfish genome, 365 million base-pairs (Mb) in length, has only one-ninth of the DNA of humans, although both vertebrate species have approximately the same number of genes. Why is there so much extra DNA in humans? Much of it appears to be in the form of introns that are substantially bigger than those in pufferfish.
See: Comparing Genomes
Amino Acid Sequence of hemoglobin:
The longstanding road map for finding the universal ancestor turns out in the light of new data to have given misleading directions, and the road map's chief author, Dr. Carl Woese of the University of Illinois, is proposing a new theory about the earliest life forms.
Scientists have been using DNA analysis to help in this excercise, but it has
turned out to be more complicated than they thought. A basic source of the confusion is that in the course of evolution whole suites of genes have apparently been transferred sideways among the major branches. Among animals, genes are passed vertically from parent to child but single-celled creatures tend to engulf each other and occasionally amalgamate into a corporate genetic entity.
Full behavioral modernity:
Klein believes that this change allowed the migration out of Africa.
The social brain hypothesis (2007) was proposed by British anthropologist Robin Dunbar, who argues that human intelligence did not evolve primarily as a means to solve ecological problems, but rather intelligence evolved as a means of surviving and reproducing in large and complex social groups.