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The Berkeley Evolution Site

Students and teachers who explore the Berkeley site will find resources to assist them in understanding and teaching evolution. The resources are organized into a variety of learning paths, such as "What did T. rex taste like?"

Charles Darwin's theory of natural selection explains how creatures that are better equipped to adapt biologically to changing environment survive over time and those that don't disappear. Science is all about this process of biological evolution.

What is Evolution?

The term "evolution" has a variety of nonscientific meanings, such as "progress" or "descent with modification." It is an academic term that is used to describe the process of changing characteristics over time in organisms or species. In biological terms the change is caused by natural selection and genetic drift.

Evolution is a central tenet of modern biology. It is an established theory that has withstood the tests of time and thousands of scientific studies. Unlike many other scientific theories, such as the Copernican theory or the germ theory of disease, the evolution theory does not address questions of spiritual belief or God's existence.

Early evolutionists, like Jean-Baptiste Lamarck and Erasmus Darwin (Charles's grandfather) believed that certain physical characteristics were predetermined to change in a step-like manner, over time. They referred to this as the "Ladder of Nature" or scala naturae. Charles Lyell first used this term in 1833 in his Principles of Geology.

Darwin published his theory of evolution in his book On the Origin of Species which was written in the early 1800s. It claims that different species of organisms share an ancestry that can be proven through fossils and other evidence. This is the current view on evolution, and is supported in a wide range of disciplines, including molecular biology.


While scientists do not know the exact mechanism by which organisms evolved but they are certain that the evolution of life on earth is the result of natural selection and genetic drift. Individuals with advantageous traits are more likely to survive and reproduce, and they transmit their genes to the next generation. In time, this results in gradual changes in the gene pool which gradually create new species and types.

Some scientists employ the term"evolution" in reference to large-scale changes, like the formation of a species from an ancestral one. Other scientists, such as population geneticists, define evolution more broadly, referring to the net change in allele frequencies over generations. Both definitions are acceptable and precise however some scientists believe that the allele-frequency definition omits essential aspects of the evolution process.

Origins of Life

The emergence of life is an essential step in evolution. The beginning of life takes place when living systems begin to develop at a micro level, like within cells.

The origins of life are one of the major topics in various disciplines that include biology, chemistry and geology. The question of how living things started is of particular importance in science because it is an important challenge to the theory of evolution. It is often referred to as "the mystery of life," or "abiogenesis."

The idea that life could arise from non-living objects was referred to as "spontaneous generation" or "spontaneous evolutionary". This was a popular belief prior to Louis Pasteur's tests proved that the creation of living organisms was not possible through an organic process.

Many scientists still think it is possible to move from nonliving to living substances. However, the conditions that are required are extremely difficult to replicate in the laboratory. Researchers investigating the beginnings of life are also interested in determining the physical properties of early Earth and other planets.

Furthermore, the growth of life is a sequence of very complex chemical reactions that cannot be predicted from the fundamental physical laws alone. This includes the conversion of long, information-rich molecules (DNA or RNA) into proteins that carry out functions and the replication of these intricate molecules to create new DNA or RNA sequences. These chemical reactions can be compared to a chicken-and egg problem that is the emergence and growth of DNA/RNA, a protein-based cell machinery, is required for the beginning of life. But without life, the chemistry needed to make it possible appears to be working.

Research in the area of abiogenesis requires collaboration between scientists from many different disciplines. This includes prebiotic chemists the astrobiologists, the planet scientists geophysicists and geologists.

Evolutionary Changes

The term "evolution" is typically used today to refer to the accumulated changes in the genetic characteristics of populations over time. These changes can result from adaptation to environmental pressures, as described in the entry on Darwinism (see the entry on Charles Darwin for background), or from natural selection.

The latter is a mechanism that increases the frequency of those genes in a species which confer an advantage in survival over other species, resulting in gradual changes in the appearance of a population. The specific mechanisms responsible for these evolutionary changes are mutation or reshuffling genes during sexual reproduction, as well as gene flow between populations.

While mutation and reshuffling of genes are common in all organisms and the process by which beneficial mutations are more prevalent is known as natural selection. As previously mentioned, those who possess the desirable trait have a higher reproduction rate than those that do not. This difference in the number of offspring that are produced over a number of generations could result in a gradual shift in the average number advantageous traits in a group.

An excellent example is the growth of the size of the beaks on different species of finches in the Galapagos Islands, which have developed beaks with different shapes that allow them to easily access food in their new environment. These changes in the shape and appearance of organisms can also be a catalyst for the creation of new species.

The majority of changes are caused by a single mutation, however sometimes multiple occur at once. Most of these changes are neither harmful nor even detrimental to the organism, however, a small proportion of them can have an advantageous impact on survival and reproduction, thus increasing their frequency in the population over time. Natural selection is a process that causes the accumulating changes over time that lead to the creation of a new species.

Many people confuse evolution with the idea of soft inheritance which is the notion that traits inherited from parents can be altered by conscious choice or abuse. This is a misinterpretation of the nature of evolution, and of the actual biological processes that lead to it. A more accurate description of evolution is that it is a two-step process that involves the distinct and often antagonistic forces of mutation and natural selection.

Origins of Humans

Humans of today (Homo Sapiens) evolved from primates, a group of mammal species that includes chimpanzees and gorillas. The earliest human fossils indicate that our ancestors were bipeds, walking on two legs. Biological and genetic similarities indicate that we have the same ancestry with chimpanzees. In fact our closest relatives are the chimpanzees of the Pan genus. This includes pygmy, as well as bonobos. The last common ancestor of modern humans and chimpanzees lived between 8 and 6 million years ago.

Humans have developed a range of characteristics over time including bipedalism, the use of fire and advanced tools. It is only in the past 100,000 years or so that the majority of the important traits that distinguish us from other species have developed. These include language, a large brain, the capacity to build and use sophisticated tools, and a the ability to adapt to cultural differences.

Evolution occurs when genetic changes allow members of a group to better adapt to the environment. Natural selection is the process that drives this change. Certain traits are preferred over others. Those with the better adaptations are more likely to pass on their genes to the next generation. This is the way all species evolve, and the basis of the theory of evolution.

Scientists refer to this as the "law of natural selection." The law states that species that share a common ancestor tend to develop similar characteristics over time. It is because these traits help them to live and reproduce in their environment.

All organisms have a DNA molecule that is the source of information that helps control their growth and development. The DNA molecule consists of base pairs that are spirally arranged around sugar molecules and phosphate molecules. The sequence of bases within each strand determines phenotype which is the person's distinctive appearance and behavior. Different mutations and reshuffling of the genetic material (known as alleles) during sexual reproduction cause variation in a population.

Fossils from the early human species Homo erectus and Homo neanderthalensis have been found in Africa, Asia and Europe. These fossils, despite a few differences in their appearance, all support the idea of modern humans' origins in Africa. Genetic and fossil evidence also suggest that early humans migrated from Africa into Asia and then Europe.

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Pub: 22 Dec 2024 13:55 UTC
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