Human Evolution Assignment PDF

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HUMAN EVOLUTION
1.)EVOLUTIONOFHUMAN
The theory of evolution by natural selection is a process by which the organisms change over
time, as a result of changes in heritable physical or behavioural traitswhich allows them to
adopt and survive in the environment. This extraordinary theory has two main aspects
according to Brian Richmond, “All life on Earth is
connectedandrelatedtoeachother,”
(Alexander,2015) and as a result of this mixture in
life "modifications of populations by natural
selection, where some traits were favoured in and
environment over others,”1. Furthermore, looking at
(Figure 1) similar ear structure and heavy bones
have been evidentbetweenwhalesand
“Indohyus”(close relative to whales)that haveaquatic
lifestyle, indicates similar traits to whales2, which
also allowed them to submerge for four minutes to
avoid predators and be able to less buoyant,. As a
consequent of organism’s connectivity due to sex
and mutation, whales ancient ancestors “pakicetids”
known from 50-million-year-old fossil had four legs
and tails which, might have looked similar to wolves
than whales due to the environment they lived in
whichfurther explains modifications of populations
by natural selection2. The two aspects mentioned
earlier are Charles Darwin’s contribution to the theory of evolution however, AlfredWallace
played a pivotal role in developing his theory. Darwin’s theory developed during the time he
spend on Galapagos island which then led him to understanding of transmutation among the
living species3. However,heobserved the absence of several species compared to ahigh
number of endemic species living on the island which was the main focus in his book called
On the Origin of Species3. According to the comparison between living species on the
island it was concluded thatsurvival of the fittestincreases probabilities of living for those
who altered their traits according to their environment3which is evident by body and trace
FIGURE1THEWHALEEVOLUTIONARYTREE
fossils (Geary, 2017). Fossils are the naturally protected body remaining of animals or plants
that lived in the geologic past4. Fossils are formed through different conditions however,
mainly fossilisation occurs in a process called petrification where skin and bones completely
decompose leaving a cast of organisms. All the found fossils of hominid are in a complex
nexus of specimens, which allows scientists to examine and study the changes occurred to
brain, body size, locomotion and other aspects of life over the past 6 million years ago6.
Moreover, examining figure 3,bipedalism and alike spinal cord structure betweenhomo,
Paranthropus, Australopithecus and Ardipithecus groupssupport changes in heritable physical
traits (evolution theory) that links them in Phylogenetic tree (figure 2)
FIGURE2
PHYLOGENETICTREE
FIGURE3SKELETONSTRUCTURE
French palaeontologist Michael Brunet lead a research team in 2001 where they uncovered
fossils of Sahelanthropus in West-Central Africa that belongs to approximately 7 million
years ago7. Thus, Brunet’s discovery proves that our ancestors were not only distributed
around the Great Rift Valley in East Africa however, more widely spread across Africa
around West-Central Africa7. Sahelanthropus had combination traits of ape-like features such
as small brain (even smaller than chimpanzee), sloping face, prominent brow ridges, and
elongated skull and human-like features such as small canine teeth, a short middle of the face,
and a spinal cord opening underneath the skull instead of towards the back as seen in non-
bipedal apes7. However, Homo sapiens evolution started in Africa approximately 300,000
years ago8. Anatomically, modern humans skeleton has a lighter bone structure compared to
early human due to our sedentary life style (Gifford, 2018).
Section 2
Examining figure 4 and 5, transformation of brain structure and size demonstrates changes in
physical and behavioural traits that allowed them to face new environmental challenges.
Thisbody adoption advanced their social interactions and unfamiliar habitats9. During the
course of human evolution brain size tripled to a more complex shape which is due to
variation of temperature (Dobzhansky, 2012). Graph 1 demonstrates the alternation of
temperature over the past 3 million years ago and during the greatest climate change the
greatest brain size increase occurs in ectotherms and endotherms. This is due to aerobic
capacity which is the main factor in physical performance, allows the brain to exponentially
grow10.
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