HUMAN EVOLUTION
Human evolution is the lengthy 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 over a period of approximately six million years. One of the earliest defining human traits, bipedalism — the ability to walk on two legs — evolved over 4 million years ago. Other important human characteristics — such as a large and complex brain, the ability to make and use tools, and the capacity for language — developed more recently. Many advanced traits — including complex symbolic expression, art, and elaborate cultural diversity — emerged mainly during the past 100,000 years.
Human evolution from its first separation from the last common ancestor of humans and chimpanzees is characterized by a number of morphological, developmental, physiological, and behavioral changes. The most significant of these adaptations are bipedalism, increased brain size, lengthened ontogeny (gestation and infancy), and decreased sexual dimorphism. The relationship between these changes is the subject of ongoing debate. Other significant morphological changes included the evolution of a power and precision grip, a change first occurring in H. erectus.
Bipedalism
There are many theories that attempt to explain why humans are bipedal. Twentieth-century theories proposed a wide array of other factors that might have driven the evolution of hominin bipedalism: carrying objects, wading to forage aquatic foods and to avoid shoreline predators, vigilantly standing in tall grass, presenting phallic or other sexual display, following migrant herds on the savanna, and conserving energy (bipedalism expends less energy than quadrupedism). Furthermore, if the early bipeds were regularly exposed to direct midday tropical sunlight, they would benefit from standing upright in two ways: less body surface would be exposed to damaging solar rays, and they would find relief in the cooler air above the ground.
Some scientists assume that the pre-bipedal primates were terrestrial quadrupeds, perhaps even knuckle-walkers like modern-day chimpanzees, bonobos, and gorillas. Conversely, it is also possible that the first habitual walkers were already well prepared for terrestrial bipedality, having adaptations for running bipedally among branches and boughs, standing upright to forage overhead, and climbing vertical tree trunks and vines. This scenario is suggested by studies of gibbons, which routinely engage in these arboreal activities and virtually never elect to move on the forest floor but, if forced to the ground, run bipedally.
Gibbons have relatively long, powerful lower limbs, the same number of lumbar vertebrae that humans have (great apes have fewer), and chests of humanoid configuration. When walking on the ground, gibbons stand up straighter than chimpanzees, which are occasionally bipedal. Moreover, they exert less energy running on the ground than when running bipedally along branches or climbing vertically. Adopting a bipedal stance with full extension of the lower limbs thus would not have been a major challenge, since all apes have this capacity, though there would have been some alteration of the lower limb bones, joints, and ligaments. The foot would probably have gone through the most dramatic change, from a prehensile organ to a heel-supported, propellent one. Increased size and frequent, sustained erect standing on extended lower limbs in order to forage overhanging branches in woodland, thicket, forest edge, and other relatively open habitats would favour the evolution of humanoid hip, knee, and foot structure. While consuming their harvests, bipedal foragers may have squatted often, thereby further selecting for robust heels and for weight distribution between the heel and forefoot and between closely placed feet. Frequent squatting and rising would enhance development of the hamstring, buttock, and anterior thigh muscles (as hip and knee extensors), which are vital for athletic bipedalism. Stretching upward would select for shorter toes and an arched foot. Refinement of the terrestrial bipedal complex probably did not occur until hominins became less dependent upon trees for daytime refuge and other activities and began to forage widely afoot and perhaps to trek seasonally over long distances.
Encephalization
The theory of encephalization is developed from elementary dimensional requirements for the construction of a brain of given size. The basic assumption in the theory is that most of the brain in vertebrates is constructed as a series of mappings repeated at various levels. Encephalization is seen as a composite of an amplification factor for the repeated mappings (identical with the encephalization quotient EQ) and a factor associated with “added” tissue. The latter may be viewed as tissue that corresponds to new functions. The relation of the theory to allometric analysis is a relationship of theory to empirical estimation of “expected” brain size at a given body size. But body size is not fundamental to the theory. It is merely one of several possible sources of a measure of the area of a basic mapping, as it were, which is then subject to the amplification factor. Issues in the use of encephalization to assess behavioral capacities are reviewed briefly, as are the neurobiological correlates of encephalization and brain size.
Sexual dimorphism
Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. .The phenomenon of sexual dimorphism is a direct product of evolution by natural selection, in that the struggle for reproductive success drives many male and female organisms down different evolutionary paths. This can produce forms of dimorphism which, on the face of it, would actually seem to disadvantage organisms. For instance, the bright coloration of male game birds makes them highly visible targets for predators, while the drab females are far better equipped to camouflage themselves. Likewise, the antlers of deer and other forms of natural weaponry are very expensive to grow and carry in terms of the energy consumed by the animal in the process.
The answer to this apparent paradox is that, at a biological level, the reproductive success of an organism is often more important than its long-term survival. This is particularly apparent in the case of game birds: a male Common Pheasant in the wild often lives no more than 10 months, with females living twice as long. However, a male pheasant’s ability to reproduce depends not on how long he lives but whether females will select him to be their mate. His bright coloration demonstrates to the female that he is fit, healthy and a good choice to father her chicks. In the case of herd animals such as deer, a male deer’s reproductive success is directly proportional to the number of sexually receptive females with which he can mate. The males’ antlers are an example of a sexually dimorphic weapon with which the males fight each other to establish breeding rights. Again, although they are expensive in terms of personal survival, they ensure that the largest and strongest males will be the most successful in reproducing and thereby ensure that those characteristics are passed on to the next generation.
Study of historical evolution of human
Pre Darwin era
The word homo, the name of the biological genus to which humans belong, is Latin for “human”. It was chosen originally by Carl Linnaeus in his Classification system. The word “human” is from the Latin humanus, the adjectival form of homo. The Latin “homo” derives from the Indo-European root “earth”. Linnaeus and other scientists of his time also considered the great apes to be the closest relatives of humans based on morphological and anatomical similarities.
Darwin’s theory
The theory of evolution by natural selection, first formulated in Darwin’s book “On the Origin of Species” in 1859, is the process by which organisms change over time as a result of changes in heritable physical or behavioral traits. Changes that allow an organism to better adapt to its Environment will help it survive and have more offspring. Evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines, including paleontology, geology, genetics and developmental biology.
The theory has two main points, said Brian Richmond, curator of human origins at the American Museum of Natural History in New York City. “All life on Earth is connected and related to each other,” and this diversity of life is a product of “modifications of populations by natural selection, where some traits were favored in and environment over others,” he said. More simply put, the theory can be described as “descent with modification,” said Briana Pobiner, an anthropologist and educator at the Smithsonian Institution National Museum of Natural History in Washington, D.C., who specializes in the study of human origins. The theory is sometimes described as “survival of the fittest,” but that can be misleading, Pobiner said. Here, “fitness” refers not to an organism’s strength or athletic ability, but rather the ability to survive and reproduce. he theory has two main points, said Brian Richmond, curator of human origins at the American Museum of Natural History in New York City. “All life on Earth is connected and related to each other,” and this diversity of life is a product of “modifications of populations by natural selection, where some traits were favored in and environment over others,” he said. More simply put, the theory can be described as “descent with modification,” said Briana Pobiner, an anthropologist and educator at the Smithsonian Institution National Museum of Natural History in Washington, D.C., who specializes in the study of human origins. The theory is sometimes described as “survival of the fittest,” but that can be misleading, Pobiner said. Here, “fitness” refers not to an organism’s strength or athletic ability, but rather the ability to survive and reproduce.,
Human evolution is the process by which humans have developed over time from earlier species. The earliest known human ancestors date back to around 7 million years ago, and the modern human species, Homo sapiens, emerged around 200,000 years ago.
Human evolution is a complex process that has been influenced by many factors, including natural selection, genetic drift, and gene flow. Natural selection is the process by which organisms that are better adapted to their environment are more likely to survive and reproduce. Genetic drift is the random change in the frequency of genes in a Population. Gene flow is the movement of genes from one population to another.
The earliest human ancestors were Australopithecines, which lived in Africa from around 4 million to 2 million years ago. Australopithecines were bipedal, meaning they walked on two legs. They had brains that were larger than those of other apes, but they were not as intelligent as modern humans.
The first species of Homo appeared around 2.8 million years ago. Homo habilis was a tool-maker, and it is thought that the development of tools was a major factor in human evolution. Homo erectus appeared around 1.8 million years ago, and it was the first species of Homo to spread out of Africa. Homo erectus was also the first species of Homo to use fire.
Homo ergaster appeared around 1.9 million years ago, and it is thought to be the ancestor of Homo erectus. Homo heidelbergensis appeared around 600,000 years ago, and it is thought to be the ancestor of Neanderthals and modern humans.
Neanderthals lived in Europe and Asia from around 400,000 to 30,000 years ago. They were physically robust, and they had brains that were larger than those of modern humans. However, they were not as intelligent as modern humans, and they eventually went extinct.
Denisovans lived in Siberia and Southeast Asia from around 50,000 to 30,000 years ago. They were very similar to Neanderthals, but they had a slightly different genetic makeup.
Modern humans, Homo sapiens, emerged in Africa around 200,000 years ago. They are the only species of Homo that is still alive today. Modern humans are the most intelligent species on Earth, and they have spread to every continent on the globe.
Human dispersal is the process by which humans have spread out over the globe. The first humans to leave Africa were Homo erectus, who migrated to Asia around 1.8 million years ago. Homo sapiens began to leave Africa around 60,000 years ago, and they eventually spread to every continent on the globe.
The peopling of Asia began with the Migration of Homo erectus from Africa to Asia around 1.8 million years ago. Homo erectus spread throughout Asia, and they eventually reached as far as China and Indonesia.
The peopling of Australia began with the migration of modern humans from Southeast Asia to Australia around 50,000 years ago. Modern humans crossed the Wallace Line, which is a biogeographical boundary that separates Asia and Australia.
The peopling of Europe began with the migration of modern humans from Africa to Europe around 45,000 years ago. Modern humans spread throughout Europe, and they eventually replaced the Neanderthals.
The peopling of the Americas began with the migration of modern humans from Siberia to North America around 15,000 years ago. Modern humans crossed the Bering Land Bridge, which is a land bridge that connected Siberia and Alaska during the last glacial period.
Human evolution after the Last Glacial Maximum was characterized by the development of agriculture, the rise of civilizations, and the Industrial revolution. Agriculture began around 10,000 years ago, and it led to the development of permanent settlements and the rise of civilizations. The Industrial Revolution began in the 18th century, and it led to the development of new technologies and the rise of the modern world.
Human evolution in the future is uncertain. Some scientists believe that humans will continue to evolve, while others believe that we will reach a point of technological advancement where we will no longer be subject to natural selection.
What is the Big Bang Theory?
The Big Bang Theory is the prevailing cosmological model for the universe. It states that the universe was once in an extremely hot and dense state that expanded rapidly. This expansion caused the universe to cool and resulted in its present size and composition.
What is dark matter?
Dark matter is a hypothetical form of matter that cannot be seen or directly detected with current instruments. It is thought to make up about 85% of the matter in the universe. Dark matter is thought to be necessary to explain the observed motion of galaxies and clusters of galaxies.
What is dark energy?
Dark energy is a hypothetical form of energy that is thought to make up about 68% of the universe. It is thought to be responsible for the accelerating expansion of the universe. Dark energy is thought to be a very weak force that acts equally on all matter and energy in the universe.
What is the speed of Light?
The speed of light is the speed at which light travels in a vacuum. It is a fundamental constant of nature and is denoted by the letter c. The speed of light is 299,792,458 meters per second.
What is the theory of relativity?
The theory of relativity is a theory of Gravitation developed by Albert Einstein between 1907 and 1915. It is one of the two pillars of modern physics (alongside quantum mechanics). The theory revolutionized our understanding of gravity and space-time.
What is quantum mechanics?
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science.
What is the double-slit experiment?
The double-slit experiment is a thought experiment that demonstrates the wave-like nature of light. In the experiment, a beam of light is shone through two slits in a barrier. The light then hits a screen behind the barrier. If light were a particle, we would expect to see two bright lines on the screen, corresponding to the two slits. However, what we actually see is an interference pattern, which is a pattern of light and dark bands. This pattern is evidence that light behaves as a wave.
What is the Higgs boson?
The Higgs boson is a subatomic particle that was first observed in 2012 at the Large Hadron Collider (LHC) at CERN. The Higgs boson is a fundamental particle, meaning that it is not made up of any smaller particles. It is also a boson, which is a type of particle that carries force. The Higgs boson is thought to be responsible for giving other particles mass.
What is the Big Crunch?
The Big Crunch is a hypothetical scenario in which the universe collapses back in on itself due to gravity. This would happen if the density of the universe is high enough. The Big Crunch would be the opposite of the Big Bang, which is the theory that the universe began with a rapid expansion.
What is the Big Freeze?
The Big Freeze is a hypothetical scenario in which the universe expands forever and eventually reaches a state of maximum entropy. This would happen if the density of the universe is low enough. The Big Freeze would be the opposite of the Big Crunch, which is the theory that the universe began with a rapid expansion.
What is the heat death of the universe?
The heat death of the universe is a hypothetical scenario in which the universe reaches a state of maximum entropy. This would happen if the universe expands forever and eventually reaches a state where all energy is evenly distributed. The heat death of the universe would be the end of time as we know it.
What is the multiverse?
The multiverse is a hypothetical theory that states that our universe is not the only one. There may be many other universes, each with its own laws of physics and constants. The multiverse is a very speculative theory, but it is one that is gaining popularity among physicists.
What is string theory?
String theory is a model of physics that attempts to unify all the forces and particles in the universe. It does this by describing all particles as tiny one-dimensional strings. String theory is a very complex theory, but it is one that has the potential to explain many of the mysteries of the universe.
Question 1
Which of the following is not a type of fossil?
(A) Trace fossil
(B) Mold fossil
(C) Cast fossil
(D) Impression fossil
Answer
(D) Impression fossil
An impression fossil is a type of trace fossil, which is a fossil that records the activity of an organism rather than the organism itself. Mold fossils and cast fossils are both types of body fossils, which are fossils that preserve the remains of an organism itself.
Question 2
Which of the following is not a type of hominid?
(A) Australopithecus
(B) Homo habilis
(C) Homo erectus
(D) Homo sapiens
Answer
(C) Homo erectus
Homo erectus is a species of hominid that lived in Africa and Asia from about 1.8 million to 117,000 years ago. It is the first hominid species to have migrated out of Africa.
Question 3
Which of the following is not a type of tool used by early hominids?
(A) Chopping tool
(B) Flake tool
(C) Hand axe
(D) Spear
Answer
(D) Spear
The spear is a tool that was first used by modern humans. Early hominids used a variety of other tools, including chopping tools, flake tools, and hand axes.
Question 4
Which of the following is not a type of fire-making technology used by early humans?
(A) Rubbing sticks together
(B) Striking flint against steel
(C) Focusing sunlight with a lens
(D) Drilling wood with a bow drill
Answer
(C) Focusing sunlight with a lens
Early humans used a variety of fire-making technologies, including rubbing sticks together, striking flint against steel, and drilling wood with a bow drill. However, they did not use lenses to focus sunlight to make fire.
Question 5
Which of the following is not a type of early human settlement?
(A) Hunter-gatherer camp
(B) Agricultural village
(C) City
(D) Town
Answer
(D) Town
Early human settlements were typically hunter-gatherer camps or agricultural villages. Towns and cities did not develop until later in human history.