- Comparative Anatomy
Evolution is the process of change over time. Rocks, cars, computers, humans- everything changes over time. So when someone asks, "What is evolution?" the real question is "What is biological evolution?" Biological evolution is descent with modification through genetic inheritance, i.e. parents pass along genetic traits to their offspring. Most importantly, biological evolution is a population process. Individuals are subject to selection and adaptation; populations evolve. Evolution may result in a new species or changes in an existing species. Generally speaking, any process that produces a shift in allele frequencies can be considered an evolutionary mechanism, including: natural selection, random mutation, genetic drift, and gene flow.
An adaptation is a characteristic with a specific function that enables an organism to live in its environment and successfully reproduce. Adaptation is also a process in which organisms adjust to their environment. Selection pressure is the force that shapes specific adaptations. Adaptation is viewed as a response to problems set by the environment, and an adaptation can be morphological (i.e. physical) or behavioral.
Gene flow is the transfer of genes from one population to another within a single species.
Mutation occurs when changes are made to the genetic material. This can occur due to a copying error during DNA replication, or exposure to radiation, chemicals, or viruses. Mutation is typically random.
Genetic drift is the accidental shift in allele frequencies in a population. It is caused by random chance as some individuals in a population leave behind a few more offspring than others. Its effects are most dramatic in small populations. The founder effect, an example of genetic drift, is seen in populations derived from a small sample of individuals who do not represent the genetic variation seen in the parent population. Genetic drift does not produce adaptations.
Natural selection one of the biggest influences on evolution. One of the processes that influence evolution is natural selection. Between individuals of a particular species there are always variations in the genetic material. Sometimes these variations give certain individuals a better chance at survival. The greater number of offspring from one individual, the greater the chance of changing the genetic structure of the population. After many generations, these small changes can add up to make an obvious difference. It has been proposed that these processes can lead to adaptation, and eventually a new species.
Both! The genetic change over time in organisms, known as biological evolution, is an observable fact which absolutely can be observed in both living organisms and in the fossil record. The "theory of evolution" commonly refers to the evolutionary mechanisms that may affect change over time within a population. A scientific theory is a hypothesis that has been tested to the extent that the observed results are reliably predictable and therefore considered true.
No. All species are related to one another because they share genetic material inherited from a common ancestor, though some species are more closely related than others. For example, human and chimpanzees share almost 98% of the same genetic material. Based on this fact, we can safely say humans and chimps shared a recent common ancestor that had ape-like morphology. This does not mean humans came from modern apes because apes living today also have evolved over millions of years since splitting from the last common ancestor with humans. The molecular data tells us that this ancestor lived between 5 and 7 million years ago. Another way to look at it, humans share nearly 85% of their DNA with mice. Eomaia scansoria was the last known common ancestor of both mice and humans and lived between 75 and 125 million years ago.
Because evolution works through the process of passing along gene variation from parent to offspring, then everything is a transitional fossil. The bigger question is in understand what characters the offspring acquired from the parent, and what traits resulted from chance mutation.
After a hominid dies, their bones settle into dirt and rocks, called sediments. They are then buried by many more layers of sediments. The weight of all these layers of sediments can sometimes crush the bones. After a long time, the calcium in the bones is replaced with minerals from surrounding soils. This process is called mineralization. It turns the bone into rock and preserves it for a long time.
Both terms are most commonly used to describe a group that includes humans and our bipedal fossil relatives. The term hominid reflects a classification that groups humans and their bipedal fossil relatives in the family Hominidea to the exclusion of apes who are placed in the families Hylobatidae (gibbon and siamang) and Pongidae (orangutan, chimpanzee, bonobo and gorilla). The term hominin reflects a classification that groups humans and chimpanzees in the subfamily Homininae and separates humans and their close fossil relatives into a separate tribe, the Hominini. Since the molecular data clearly shows a close genetic relationship between humans and chimpanzees, it is more appropriate to use the term hominin when discussing human evolution.
Most often a team of scientists (including anthropologists, geologists, archaeologists, etc.) meticulously excavate a particular locality in hopes of finding fossils. In other cases, fossils are found by pure accident and are later brought to scientists’ attention for inspection and investigation.
Hominins didn't live in houses like modern humans. Instead, hominins most likely spent the night in trees or in caves. It is not known exactly when hominins began living in permanent shelters.
Some hominins (relatively recently in geologic time) been discovered along with evidence of tool use — tools found in situ with hominin fossils. Based on these localities, it is possible to infer that other hominins used tools as well, even if there is no evidence for tool use found with the fossils. It is important to remember that sone tools are often durable enough to survive burial, and resistis erosion and weathering. Other tools, such as wood sticks, are not likely to survive in the archaeological record, but that does not mean they weren't created and utilized by hominins.
There is no evidence that hominins had a spoken language, however, they may have been able to communicate in different forms. There is documented proof that primates communicate in a variety of ways such as using gestures, facial expressions and vocalizations. Humans communicate this way as well. For example, a smile is often interpreted as a sign of happiness.
Absolute brain size is the actual size of the brain. Relative brain size is the size of the brain compared to the size of the entire body. Both absolute and relative brain size can help anthropologists differentiate between species.
Not necessarily. Relative brain size is simply the size of the brain relative to the rest of the body. Absolute brain size is not necessarily a diagnostic factor of intelligence. For example, Neanderthals had a larger body size than modern humans, which was an adaptation to colder climates. This means Neanderthals also had a larger brain size, but it doesn't mean they were more intelligent than modern humans.
Bone is made up of both organic and inorganic components. Protein collagen provides the flexibility of bones while the mineral components of bones are mostly hydroxyapatites, formed primarily of calcium and phosphorus. Small amounts of sodium, magnesium, fluorides, and carbonates are also present. One-third of living bone is water.
No. Most adult men and women have 12 pairs of ribs. However, there is variation in this number and some people may have an extra pair of ribs or an extra vertebra.
A fossil is any anatomical evidence of past life. There are many different types of fossils, including body fossils where part(s) of the skeleton is preserved; trace fossils that preserve evidence of behavior such as footprints; and extraordinary fossils where soft tissues, such as skin, are preserved. Different types of processes are involved in the formation of different types of fossils.
A species is a group of interbreeding or potentially interbreeding organisms capable of producing fertile offspring. All offspring inherit genetic material from their parents, with individuals experiencing genetic mutations that make them slightly different from their parents. New species form when a population (i.e. daughter population) experiences genetic change due to an environmental or genetic factor that inhibits successfully reproduction with members of the ancestral (i.e. parent) population. This is commonly referred to as a speciation event. In cases where the species is extinct and known only from the fossil record, scientists can classify the fossil into a species based on traits that make fossil specimens unique from one another. In more recent years, scientists have used DNA analysis to differentiate between species.
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