Biological Anthropology Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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- A -

abdominal wall defect  click this icon to hear the preceding term pronounced
a genetically inherited condition in which intestines and other abdominal organs protrude through the central abdominal wall.  This must be corrected by surgery at birth.
ABO click this icon to hear the preceding term pronounced blood system
a human blood typing system in which there are 4 distinct types: A, B, AB, and O.  An individual inherits an ABO type from his or her parents and does not change it throughout life.  The ABO system is not unique to humans but is shared by many other primates including apes and monkeys.  Humans and other primates share other blood typing systems as well.
accelerator mass spectrometer  click this icon to hear the preceding term pronounced   (AMS)
a research instrument primarily used in physics to accelerate streams of charged subnuclear particles to high velocities in order to sort and analyze them.  This technique is now also used to count carbon isotope atoms for radiocarbon dating.  The advantage of this technique over the conventional radiocarbon method is that it requires a far smaller sample size and can potentially provide dates going back to around 100,000 B.P.  At present, however, AMS dates generally are for events less than 60,000 years old.
acclimatization  click this icon to hear the preceding term pronounced
changes in the body in response to environmental stresses such as high or low temperatures, intense ultraviolet radiation from sun light, or high altitude.  The anatomical and physiological changes made in acclimatization are usually reversible.
Acheulian click this icon to hear the preceding term pronounced tool tradition
the most well known stone tool making tradition of Homo erectus and early archaic Homo sapiens.  It first appeared about 1.5 million years ago or somewhat earlier in East Africa and eventually spread throughout Africa, Southern Europe, and South Asia.  The most diagnostic Acheulian artifact is the hand ax.
adaptation  click this icon to hear the preceding term pronounced
the process by which populations of organisms respond to long term environmental stresses by permanent genetic change--i.e., by evolving.  See adjustment.
adaptive radiation  click this icon to hear the preceding term pronounced
the relatively rapid expansion and diversification of an evolving group of organisms as they adapt to new ecological niches.  Adaptive radiation is the process by which one species evolves into two or more species.  This occurs as a result of different populations becoming reproductively isolated from each other, usually by adapting to different environments.  The branching pattern of evolution resulting from adaptive radiation is known as cladogenesis click this icon to hear the preceding term pronounced.
adjustment
the process by which individual organisms respond to environmental stresses during their lifetime without changing genetically.  Adjustments are generally not inheritable.  Acclimatization and developmental adjustment are examples of adjustment.  See adaptation.
agglutination  click this icon to hear the preceding term pronounced
the clumping together of red cells in blood as a result of antibodies attaching to antigens on the surface of the cells.  This occurs when blood of incompatible types is mixed together outside of the body, as for example during blood typing.  When different types of blood come into contact within the body as a result of a mismatched transfusion, the alien red cells usually burst instead of agglutinate.
agonistic display  click this icon to hear the preceding term pronounced
a threatening gesture, stare, pose, or display intended to intimidate others.
AIDS  click this icon to hear the preceding term pronounced   (Acquired Immunodeficiency Deficiency Syndrome)
a slow acting disease caused by the HIV retrovirus.  AIDS is usually fatal if not treated.  Important disease-fighting white blood cells are destroyed, resulting in a weakened immune system.  Death usually comes as a result of cancer or other diseases that are normally fought off by healthy immune systems.  HIV is spread from person to person via bodily fluids such as blood and semen.  The common methods of transmission are via sexual intercourse or sharing hypodermic needles.
albinism  click this icon to hear the preceding term pronounced
the genetically inherited condition in which there is a marked deficiency of pigmentation in skin, hair, and eyes.  An individual with these traits is an "albino."  Since the gene for albinism is recessive, it only shows up in the phenotype of homozygous recessive people.  Albinos have sunlight sensitive eyes and skin.  They are also more likely to develop skin and eye cancers.  This is a pleiotropic trait.

allele  click this icon to hear the preceding term pronounced

an alternate form or variety of a gene.   The alleles for a trait occupy the same locus or position on homologous chromosomes and thus govern the same trait.  However, because they are different, their action may result in different expressions of that trait.
Allen's Rule  click this icon to hear the preceding term pronounced
within the same species of warm-blooded animals, individuals from populations living in colder environments usually have shorter appendages than do those from populations in warmer areas.  This is because of the selective advantage it provides.  Short arms, legs, and other appendages have relatively less skin surface area that can radiate heat into the surrounding environment.  Subsequently, the body retains more of it.   Allen's Rule is a corollary of Bergmann's Rule.  Allen's  Rule was named after Joel Allen, a 19th century naturalist. 
allogrooming  click this icon to hear the preceding term pronounced
the common primate practice of carefully picking through the hair of someone, looking for insects, twigs, and other debris.  Grooming others is a common way by which primates communicate affection and reduce group tension.  See autogrooming.
alpha-feto protein (AFP) sampling  click this icon to hear the preceding term pronounced
a routine diagnostic procedure for pregnant women to determine whether or not their fetuses have gross chromosomal anomalies.  This screening procedure is also called maternal serum alpha-feto protein (MSAFP) testing.  The testing is comparatively inexpensive but not as reliable as amniocentesis or chorionic villi sampling.  With AFP sampling, blood is drawn from a pregnant woman in order to determine the amount of alpha-feto protein that has leaked into her system from her unborn child.  Unusually high or low amounts of AFP relative to the stage of pregnancy indicates that there may be specific kinds of genetic defects.  Specifically, it may indicate the likelihood of Down syndrome, neural tube defects, abdominal wall defects, and trisomy 18.  Low AFP levels are associated with Down syndrome, while high levels are indicative of neural tube defects.  The amounts of other diagnostic fetal chemicals (hCG and estriol) also are measured in expanded AFP screening or triple-screening.
alpha male click this icon to hear the preceding term pronounced and alpha female
the adult male and female members of a community who are at the top of their gender based dominance hierarchies.  Non-human primate alpha males and females usually mate more frequently and have greater access to food.
alpha particle  click this icon to hear the preceding term pronounced
a kind of positively charged subnuclear particle (consisting of 2 protons and 2 neutrons) given off by some isotopes when they decay or fission.
Alzheimer syndrome  click this icon to hear the preceding term pronounced
a progressive, irreversible disease characterized by degeneration of brain cells that commonly result in severe loss of memory, the ability to think, and pay attention.  There are also usually major changes in personality.   Alzheimer syndrome most often occurs in late middle and old age.  Genetic factors probably play a role since this syndrome is more common in some families. 
amino acid  click this icon to hear the preceding term pronounced
an organic molecule that is a building blocks of proteins.  There are at least 20 different kinds of amino acids in living things.  Proteins are composed of different combinations of amino acids assembled in chain-like molecules.  Amino acids are primarily composed of carbon, oxygen, hydrogen, and nitrogen.
amino acid racemization click this icon to hear the preceding term pronounced dating
a method for dating organic matter that is based on the fact that amino acids progressively change to mirror image forms following the death of an organism--i.e., from L-amino acid to D-amino acid forms.  Aspartic acid in organic samples is commonly used for this dating technique.  Amino acid racemization could be considered to be a chronometric or a calibrated relative dating method.
Amish  click this icon to hear the preceding term pronounced
members of a conservative Protestant sect related to the Mennonites.  The Amish migrated to Pennsylvania from Switzerland in the late 18th century.  The Old Order Amish are a relatively closed group that shun most modern conveniences in their farming lifestyle.  They use horse drawn carriages, dress very simply, and reject those who marry non-Amish.
amniocentesis  click this icon to hear the preceding term pronounced
a diagnostic procedure for pregnant women to determine whether or not their fetuses have gross chromosomal anomalies.  It involves sampling the liquid immediately surrounding a fetus within the amnion.  This amniotic fluid is extracted through the mother's abdominal and uterine walls with a hypodermic needle.  The amniotic fluid mostly contains fetal urine but also has millions of fetal skin cells that can be cultured to produce a karyotype.  There is 99+% accuracy in diagnosing Down syndrome and most other gross chromosomal aberrations including neural tube defects such as spina bifida.
amnion  click this icon to hear the preceding term pronounced
the innermost membrane of the flexible sac enclosing a fetus.  It is filled with amniotic fluid, which helps cushion the fetus and protect it from injury.  See cervix for an illustration.
amniote  click this icon to hear the preceding term pronounced
referring to an egg with a hard shell and protective membranes that prevent the embryo from rapidly drying out.  Reptiles, birds, and prototherian mammals lay amniote eggs.
amniotic fluid  click this icon to hear the preceding term pronounced
the fluid surrounding a fetus inside an amniotic sac.  It mostly consists of fetal urine, but also contains some fetal skin cells.  See cervix for an illustration.
Amphibia  click this icon to hear the preceding term pronounced
the class of vertebrates that includes frogs, toads, and salamanders.  Amphibians spend part of their lives under water and part on land.  They must return to damp areas to reproduce since their eggs would otherwise dry out.  They start life with gills, like fish, and later develop lungs to breath air.
anaerobic  click this icon to hear the preceding term pronounced
without oxygen
anagenesis  click this icon to hear the preceding term pronounced
The pattern of non-branching evolution that results from successive speciation in a single evolutionary line.
analogies  click this icon to hear the preceding term pronounced
anatomical features that have the same form or function in different species that have no known common ancestor.  Analogies are also referred to as analogous structures or features.
analogous structures  click this icon to hear the preceding term pronounced
see analogies.

anatomy  click this icon to hear the preceding term pronounced

referring to the structural parts of organisms.  See physiology.
anemia  click this icon to hear the preceding term pronounced
a medical condition characterized by fatigue, weakness, poor appetite, weight loss, and paleness or a yellowish tinge to the skin and eyes resulting from a deficiency of red blood cells or insufficient amounts of hemoglobin molecules within the red cells.  The result in both cases is a significantly reduced ability to get oxygen to the cells of the body.  There are many different genetic and environmental causes of anemia.
anencephaly  click this icon to hear the preceding term pronounced
the failure to develop a brain at the end of the spinal chord.   This type of neural tube defect always causes the death of a fetus or newborn child.
aneuploidy  click this icon to hear the preceding term pronounced
a chromosomal abnormality in which there is an addition or loss of chromosomes within a set (e.g., 23 + 22 or 23 + 24).  Down syndrome is most often the result of this kind of error.  See monosomy, trisomy, and polyploidy.

Angelman syndrome  click this icon to hear the preceding term pronounced

a rare genetically inherited form of mental retardation.  The inheritance of this syndrome is subject to genome imprinting.
angle of declination  click this icon to hear the preceding term pronounced
the degree difference between the direction of magnetic north and rotational north at a particular location.
Animalia  click this icon to hear the preceding term pronounced
the kingdom of living things that includes all animals. They are multicellular organisms that ingest food rather than absorb or photosynthesize it.  They also have their own means of locomotion in at least one phase of their life cycles.
anterior  click this icon to hear the preceding term pronounced
see dorsal.
anthropoid  click this icon to hear the preceding term pronounced
an animal within the primate suborder Anthropoidea click this icon to hear the preceding term pronounced.  Monkeys, apes, and humans are anthropoids.

antibody  click this icon to hear the preceding term pronounced

a kind of protein produced by the body to identify and neutralize or destroy alien antigens.  Antibodies are involved in the rejection of mismatched blood transfusions and organ transplants.  They are also responsible for recognizing and eliminating bacteria and viruses.  Antibodies provide a major defense for our bodies against invasion by alien organisms.

anticodons  click this icon to hear the preceding term pronounced

sequences of three nucleotide bases on a transfer RNA molecule that can pair with a specific messenger RNA Codon.

antigen  click this icon to hear the preceding term pronounced

molecules that provide the specific signature or identity to blood or other tissue cells.  When alien antigens are introduced into the body, they stimulate the production and mobilization of antibodies.  Antigens are found on the surface of blood and other tissue cells as well as bacteria and viruses.
apparent temperature
what the air temperature actually feels like to people.  This varies with the relative humidity of the air.  The higher the relative humidity, the higher the apparent temperature is even if the air temperature does not change because evaporation of sweat is progressively less efficient in cooling the body.
arboreal  click this icon to hear the preceding term pronounced
tree-living; referring to animals that are adapted to life in the trees.  Arboreal animals spend most of their time scampering around in trees rather than on the ground, in the air, or water.  See semi-terrestrial and terrestrial.
archaeology  click this icon to hear the preceding term pronounced
the study of the prehistory or early history of societies and their cultures.  Unlike paleoanthropology, the focus of archaeology is mainly on the material remains of culture rather than biological evolution.
archaeomagnetic click this icon to hear the preceding term pronounced dating
See paleomagnetic dating.
archaic Homo sapiens  click this icon to hear the preceding term pronounced
the variety or species of humans that was intermediate between Homo erectus and modern humans.  The earliest archaic Homo sapiens may have appeared before 600,000 years ago in Southern Europe and Northwest Africa.  Elsewhere in the Old World, the transition to archaic Homo sapiens began around 400,000 years ago or later.  The most well know archaic Homo sapiens were the Neandertals.  Archaic Homo sapiens are also known as archaic humans and early Homo sapiens.  See Homo heidelbergensis.
argon-40/argon-39 click this icon to hear the preceding term pronounced dating   (40Ar/39Ar)
a radiometric dating method based on the changing ratio of argon-40 to argon-39  with the passage of time in volcanic rock or ash.  This technique was derived from potassium-argon dating.  The argon-40/argon-39 method is usually more accurate than potassium-argon dating and doesn't require as large a sample.
arthritis  click this icon to hear the preceding term pronounced
a degenerative disease characterized by chronic inflammation of the joints and accompanying pain. 
artifact  click this icon to hear the preceding term pronounced
a thing that is intentionally made according to a cultural pattern or inadvertently modified as a result of culturally patterned behavior.  Artifacts are usually relatively portable objects such as projectile points, ceramic pots, and baskets.
artifact time marker
an artifact type that was made by a particular culture during a limited time period.  When discovered clearly in association with ancient humans in an archaeological site, they are an indication of at least the relative time of the occupation.  When the independent dating of the artifact types is reliable, this can be considered a calibrated relative dating method.
assimilation model
a hypothesis to explain the origin of modern Homo sapiens.  It proposes that the first modern humans evolved in Africa, but when they migrated into other regions they did not simply replace existing human populations.  Rather, they interbred to a limited degree with late archaic Homo sapiens resulting in hybrid populations.  The assimilation model is also known as the "partial replacement model."  See replacement model and regional continuity model.
atlatl  click this icon to hear the preceding term pronounced
see spear thrower.
australopithecine  click this icon to hear the preceding term pronounced
a species of the genus Australopithecus.   They lived during the Pliocene and early Pleistocene geological Epochs in Africa (i.e., ca. 4.2-1.4 million years ago).  Australopithecines and humans are hominins.  One or more species of australopithecines probably were our ancestors.
Australopithecus  click this icon to hear the preceding term pronounced
see australopithecines
autogrooming  click this icon to hear the preceding term pronounced
grooming oneself in contrast to allogrooming.
autoimmune disorder  click this icon to hear the preceding term pronounced
any of several disorders in which one's antibodies attack his/her own body tissues.  Lupus erythematosus, rheumatoid arthritis, and even common allergies are caused by such autoimmune reactions.
atomic mass
the mass number of one atom of an isotope (e.g., carbon-14).  It is the sum of the number of protons and neutrons in the nucleus of one atom.  See atomic number.
atomic number
the number of protons in the nucleus of one atom of an element.  See atomic mass.

autosome  click this icon to hear the preceding term pronounced

any chromosome other than a sex chromosome.  Human somatic cells have 22 pairs of autosomes and 1 pair of sex chromosomes.
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- B -

bacteria  click this icon to hear the preceding term pronounced
microscopic simple single celled organisms lacking chlorophyll and a membrane around their nuclei.  They reproduce by mitosis.  Many species of bacteria are parasites of humans and other animals and plants.  Bacteria are classified as members of the Kingdom Monera.  
balanced polymorphism  click this icon to hear the preceding term pronounced
the maintenance of two or more alleles for a trait in a population at a more or less constant frequency ratio due to the selective advantage of heterozygotes.  See polymorphism.
basal metabolic rate  click this icon to hear the preceding term pronounced
the measure of the total energy utilized by the body to maintain its necessary processes while at rest.  Those processes include  keeping the heart, brain, and other organs functioning normally and the necessary replacement of old or damaged cells.  About 75% of the food energy that we burn every day is used for these functions.  The remaining energy is used to fuel physical work or is stored in fat reserves for when it is needed.  Basal metabolic rate also refers to the minimum level of heat produced by the body at rest.
Bergmann's Rule  click this icon to hear the preceding term pronounced
within the same species of warm-blooded animals, individuals from populations living in colder environments usually have greater body mass than do those from populations in warmer areas.  This is because of the selective advantage it provides.  A massive body produces more internal heat and radiates relatively less of it into the surrounding environment because the skin surface area is relatively smaller.  Subsequently, a massive body produces and retains more heat.    Bergmann's Rule was named after Carl Bergmann, a19th century naturalist.  See Allen's Rule.
Beringia  click this icon to hear the preceding term pronounced
the intercontinental land connection appeared between Siberia and Alaska that appeared at least twice during the last ice age as a result of sea levels dropping more than 300 feet.  Beringia is also known as the Bering Plain.
Bering Plain
see Beringia.
beta particle  click this icon to hear the preceding term pronounced
a kind of energy charged subnuclear particle (consisting of an electron or a positron) given off by some isotopes when they decay or fission.
biface  click this icon to hear the preceding term pronounced
a stone tool that is shaped on two faces or sides.  Hand axes are examples of bifaces.  See uniface.
big game hunting
a specialized subsistence pattern based primarily on hunting large animals, especially herbivorous herding mammals such as horses, reindeer, bison, and elephants.
bilaterally symmetrical  click this icon to hear the preceding term pronounced
the chordate characteristic of the left and right sides of the body being mirror images of each other.  If there are two functionally similar body parts, they are usually found roughly equidistant from the center line, parallel to each other on bilaterally symmetrical animals.
bilirubin  click this icon to hear the preceding term pronounced
the yellow-red pigment of human bile.  Small amounts of it are normally found in blood and urine.  At high bilirubin levels, blood and urine change color and the skin becomes yellow or jaundiced.  This is one of the symptoms of mismatched blood transfusions and mother-fetus incompatibility in blood type.
binocular vision  click this icon to hear the preceding term pronounced
seeing with two eyes that have an overlapping field of view.  This is essential to stereoscopic vision.
binomen  click this icon to hear the preceding term pronounced
the Linnaean classification system use of two Latin name categories, genus and species, to designate each type of organism.  A genus is a higher level category that includes one or more species under it.  For example, humans are Homo sapiens, or "man who is wise"--Homo is our genus and sapiens is our species.  Binomen literally means "two names" in Latin.  Binomial nomenclature is another term for binomen. 
binomial nomenclature  click this icon to hear the preceding term pronounced
see binomen.
biocultural evolution  click this icon to hear the preceding term pronounced
the pattern of human evolution in which the effects of natural selection are altered by cultural inventions.  Culture can alter the direction of evolution by creating non-biological adaptations to environmental stresses (e.g., wearing insulating clothes on very cold days).  This potentially reduces the need to evolve genetic responses to the stresses.  This has meant that we have been able to remain essentially tropical animals biologically and live in colder regions of our planet.  Biocultural evolution can also involve a mutual, interactive evolution of human biology and culture.   An example of this has been the selection favoring sickle-cell trait in Africa.  Human agricultural practices altered the environment, which resulted in factors that were advantageous to both the malarial microorganisms and the mosquitoes that transmit them between people.  This, in turn, selected for the sickling allele. 
biopsy  click this icon to hear the preceding term pronounced
the process of removing a tissue sample from a living organism for diagnostic examination (e.g., chorionic villi sampling).
biospecies  click this icon to hear the preceding term pronounced
a species that has been defined on the basis of the ability to produce fertile offspring.  Members of the same species can produce offspring that can in turn reproduce while members of different species cannot.  See morphospecies.
biostratigraphy  click this icon to hear the preceding term pronounced
the relative dating of early human sites by association with index fossils uncovered in the same strata as human evidence.  The assumption is that both the people and the species that is now an index fossil must have lived at about the same time.
bipedalism  click this icon to hear the preceding term pronounced
referring to walking and running on two feet.  Humans are the only fully bipedal primates today.
blade flake  click this icon to hear the preceding term pronounced
a thin, roughly parallel-sided stone flake that is at least twice as long and it is wide.  They were made out of brittle breaking materials such as flint click this icon to hear the preceding term pronounced, chert click this icon to hear the preceding term pronounced, and obsidian click this icon to hear the preceding term pronounced.  Blade flakes were preforms for the manufacture of many different kinds of tools during the Upper Paleolithic--e.g., knives, hide scrapers, spear tips, drills, awls, and burins.  See punch flaking.

blending theory

an incorrect 19th century theory about the inheritance of characteristics.  It proposed that inherited traits blend from generation to generation.  Through his plant cross-breeding experiments, Gregor Mendel proved that this was wrong.
body language
gestures, postures, and facial expressions used to communicate nonverbally.

bottleneck effect

a dramatic reduction in genetic diversity of a population or species resulting from an ecological crisis that wipes out most of its members.  The limited genetic diversity of the few survivors is the pool from which all future generations are based.  This is one of the small population size effects.
B.P. date  click this icon to hear the preceding term pronounced
a chronometric date that is measured in years before the present.  By convention, scientists have assigned 1950 A.D. in the Gregorian calendar as the present.
brachiator  click this icon to hear the preceding term pronounced
an animal that travels through the trees by swinging under branches with a hand over hand motion.  The smaller apes and some New World monkeys brachiate.  Brachiation is also referred to as suspensory climbing.
Broca's area  click this icon to hear the preceding term pronounced
a small area of the human brain that controls the production of speech.  It is located in the left frontal lobe of the cerebral cortex click this icon to hear the preceding term pronounced.  See Wernicke's area.

bubonic plague  click this icon to hear the preceding term pronounced

a highly contagious disease caused by the bacterium Yersinia pestis.  It is normally spread by fleas that have taken blood from an infected human or other animal.  Symptoms include a high fever and extremely swollen lymph nodes in the groin, armpits, and/or throat.  An agonizing death usually occurs within a few days.
bull roarer
a musical instrument or noise maker consisting of a flat, elongated oval slab of rock, bone, or wood with a hole in one end through which a string is attached.  When it is twisted and then whirled rapidly by the string, a humming or "roaring" noise is produced.  Bull roarers may be only a few inches in length or several feet long.
burin  click this icon to hear the preceding term pronounced
narrow gouging chisels used to make and shape a host of other implements out of bone, tusks, antler, or wood.  They were usually made from blade flakes in the late Upper Paleolithic tool traditions. 

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- C -

calibrated relative dating
use of a relative dating method that measures somewhat irregular occurring natural phenomena that have been cross-dated with at least one chronometric technique so that the dates are somewhat comparable from sites in one region to another.  Calibrated relative methods could be considered to be somewhere between ordinary relative methods and radiometric methods in terms of their ability to produce dates that closely approximate the actual date of a sample.  Amino acid racemization and paleomagnetic dating are generally considered to be either chronometric or calibrated relative methods. 
canine click this icon to hear the preceding term pronounced teeth
the comparatively pointed teeth on either side of the incisors, at the front of the mouth of mammals.  There is one canine tooth in each of the four quadrants of the mouth.  Canine teeth are mainly used to pierce and tear food.  See molar and premolar teeth.
canine diastema    click this icon to hear the preceding term pronounced
a space or gap between the canine and adjacent teeth.  It allows room for the point of the protruding opposite canine tooth and thereby permits the upper and lower teeth to bite together.  Normally, there is a diastema opposite each of the four canine teeth if the canines are significantly longer than the other teeth.
capillaries  click this icon to hear the preceding term pronounced
the hair thin blood vessels connecting small branches of arteries and veins that form a vascular network throughout the body of animals.
carbohydrate  click this icon to hear the preceding term pronounced
a class of organic molecules that include sugars and starches.
carbon-14 dating   (C-14 click this icon to hear the preceding term pronounced)
see radiocarbon dating.
carnivorous  click this icon to hear the preceding term pronounced
eating only meat.  Animals that have this sort of diet are carnivores.  See herbivorous and omnivorous.
carotene  click this icon to hear the preceding term pronounced
any of several reddish-orange organic pigments.  While carotene is present in human skin, it is also found in higher concentrations in butter, carrots, and some other vegetables.  Carotene is involved in the synthesis of vitamin A in people and other animals.
carrier
an individual who is heterozygous for a trait that only shows up in the phenotype of those who are homozygous recessive.  Carriers often do not show any signs of the trait but can pass it on to their offspring.  This is the case with hemophilia.
cataract  click this icon to hear the preceding term pronounced
an impairment of vision caused by the lenses of the eyes becoming cloudy.  Cataracts are common in elderly people.  They may be inherited or caused by diabetes and environmental factors.
catastrophism  click this icon to hear the preceding term pronounced
the view that the Earth's geological landscape is the result of violent cataclysmic events.  Advocates of this theory usually believe that there have been a number of wide-spread violent and sudden natural catastrophes that have destroyed most living things.  This idea was used by George Cuvier to explain the extinction of species.   Catastrophism was opposed by uniformitarianism during the late 18th and 19th centuries.
Caucasoid  click this icon to hear the preceding term pronounced   (or Caucasian click this icon to hear the preceding term pronounced)
a presumed human "race" consisting of Europeans and other closely related people. The classification is based on the discredited typological model.  The term "Caucasoid" was derived from the Caucasus Mountains on the southeast fringe of Europe between the Black and Caspian Seas.  This region was once thought to be the homeland of Indo-Europeans.
cell  click this icon to hear the preceding term pronounced
a complex unit of protoplasm, usually with a nucleus, cytoplasm, and an enclosing membrane. All plants and animals are composed of one or more microscopic cells.  The smallest organic unit capable of carrying out all of the functions normally attributed to life is a cell.  See eukaryotic cell and prokaryotic cell.
cell membrane  click this icon to hear the preceding term pronounced
the selectively permeable membrane enclosing a cell.
Cenozoic Era  click this icon to hear the preceding term pronounced
the most recent geological era, dating from about 65.5 million years ago to the present.  It is the era in which the mammals flourished.  It began as the last dinosaurs became extinct, at the end of the Mesozoic Era.  Most of the placental mammals and all of the primates evolved during the Cenozoic.
centriole  click this icon to hear the preceding term pronounced
small, dense bodies outside of a cell nucleus that contract and become visible early in mitosis and meiosis when the nuclear membrane breaks down.  Spindle fibers eventually emanate from each centriole and connect to the centromeres of chromosomes.
centromere  click this icon to hear the preceding term pronounced
a constriction in a chromosome where two or more chromatids come together.
cerebral cortex   click this icon to hear the preceding term pronounced
the outer portion of a brain's cerebrum.  This is the area associated with coordination of sensory and motor information as well as higher thought processes.
cerebral edema  click this icon to hear the preceding term pronounced
an abnormal accumulation of fluid around the brain causing it to swell.  This potentially life threatening condition can be caused by hypoxia at high altitude.  See pulmonary edema.
cerebrum  click this icon to hear the preceding term pronounced
the two large frontal lobes at the top of the brain that make up about 85% of its weight in modern humans.  Our high level mental functions, such as speech and processing complex information, occur in the cerebrum.  The cerebral cortex, or outer surface, is deeply convoluted.  About 2/3 of the human brain surface lies within these folds.  The amount of cerebral cortex folding, and subsequently the surface area of the brain, increased as humans evolved from Homo habilis to Homo erectus and ultimately Homo sapiens.
cervix  click this icon to hear the preceding term pronounced
the neck-like opening at the lower end of the uterus that connects to the vagina.
cheek pouches
cheeks that are so elastic that they can expand to allow temporary storage of food.  This is useful when there is competition.  Old World monkey in the subfamily Cercopithecinae (macaques, baboons, etc.) have cheek pouches of this sort.
chimera  click this icon to hear the preceding term pronounced     (also spelled chimaera)
an individual who is genetically two people.  Fully chimeric individuals are usually the product of two fertilized ova fusing into a single embryo shortly after conception.
Chordata  click this icon to hear the preceding term pronounced
the phylum of animals that is characterized by elongated bilaterally symmetrical bodies.  In some phase of their life cycle, they have a notochord and gill slits or pouches. Chordates also often have a head, a tail, and a digestive system with an opening at both ends of the body. The Chordata include fish, amphibians, reptiles, birds, mammals, and 2 invertebrate subphyla (tunicates and lancelets).
chordate  click this icon to hear the preceding term pronounced
a member of the phylum Chordata.
chorion  click this icon to hear the preceding term pronounced
The membrane that develops around an embryo and contributes to the formation of the placenta.  Later, as a fetus develops, the chorion fuses with the amnion.  See chorionic villi sampling for an illustration.
chorionic villi sampling  click this icon to hear the preceding term pronounced   (or biopsy click this icon to hear the preceding term pronounced)
a diagnostic procedure for pregnant women to determine whether or not their fetuses have gross chromosomal anomalies.  It involves collecting a small sample of chorion cells for karyotyping.  The biopsy usually is done by inserting a small flexible plastic tube through the vagina and the cervix of the uterus to draw out a sample of chorion tissue.   Alternately, the cells may be extracted with a hypodermic needle through the uterine wall, as in the case of amniocentesis.   With CVS, there is approximately 98% accuracy in diagnosing Down syndrome and many other conditions due to gross chromosomal abnormalities.  However, the accuracy in predicting neural tube defects is lower than with amniocentesis.  Some sources refer to CVS as "chorionic villus sampling".  "Villus" is the singular of "villi".
chromatids  click this icon to hear the preceding term pronounced
one of two or more strands of a chromosome that are joined at a centromere.
chromosome  click this icon to hear the preceding term pronounced
a discrete, thread-like, gene-carrying body in the nucleus of a cell.  Chromosomes are composed primarily of DNA and protein.  They are visible only under magnification during certain stages of cell division.  Humans have 46 chromosomes in each somatic cell and 23 in each sex cell.
chronic disease
an illness that lasts for a long period of time or indefinitely.  In contrast, an acute disease is one with a rapid onset and a short but usually severe course.
chronometric click this icon to hear the preceding term pronounced date
a date that places an event in its chronological position with reference to a universal time scale such as a calendar.   Such dates usually are given in terms of the number of years before or after a calendar starting point.  For instance, 1950 B.C. was 1950 years before the beginning date of the Gregorian calendar, which is commonly used today.  Chronometric dating methods include the use of written records, dendrochronology, and radiometric methods.  See relative date.
cladistics  click this icon to hear the preceding term pronounced
an approach to discovering evolutionary relationships between organisms based on shared derived traits.  Cladistics has largely replaced the older approach known as evolutionary or phylogenetic sytematics which grouped organisms together based on homologies in general without distinguishing between primitive and derived ones.
cladogenesis  click this icon to hear the preceding term pronounced
the branching pattern of evolution resulting from adaptive radiation.
class
the level of classification below subphylum and above subclass in the Linnaean classification system.  Humans are members of the class Mammalia.
clavicles  click this icon to hear the preceding term pronounced
collarbones; the bones that connect the sternum with the scapula.  A single clavicle on each side of the body goes from the center of the upper chest to the shoulders.
clinal model  click this icon to hear the preceding term pronounced    (of human variation)
a system for classifying people based on the knowledge that genetically inherited traits often gradually change in frequency from one geographic region to another--that is, they change in clines.
clines  click this icon to hear the preceding term pronounced
progressively changing zones of degree difference in frequency of a trait with movement from one region to another.  The gradual decrease in frequency of the B blood allele going west in Europe is an example of such a gradation or clinal distribution.  See discontinuous distribution.
codominance  click this icon to hear the preceding term pronounced
the situation in which two different alleles for a trait are expressed unblended in the phenotype of heterozygous individuals.  Neither allele is dominant or recessive, so that both appear in the phenotype or influence it.  Type AB blood is an example.  Such traits are said to be codominant.
codon  click this icon to hear the preceding term pronounced
a sequence of three nucleotide bases in a DNA or RNA molecule that code for a specific type of amino acid that will be used in the synthesis of a protein.
collarbones
see clavicles.
color blindness
the inability to see certain colors as they normally appear to others.  The most common form of this vision deficiency is X-linked genetically inherited red-green color blindness.
conduction  click this icon to hear the preceding term pronounced
the movement of heat from one object to another by direct contact.  Example: the transmission of heat from your body to the chair on which you are sitting.  See convection and radiation.
consanguineous mating  click this icon to hear the preceding term pronounced
the mating of closely related individuals, such as brothers, sisters, or cousins.  Another name for this mating pattern is "inbreeding."  This is an extreme form of positive assortative mating.
convection  click this icon to hear the preceding term pronounced
the movement of heat from on object to the surrounding fluid (either gas or liquid).  Example: the transmission of heat from your body to water when you are swimming.  See conduction and radiation.
convergence  click this icon to hear the preceding term pronounced
the development of a similar anatomical feature in distinct species lines after divergence from a common ancestor that did not have the initial trait that led to it.  The common ancestor is usually more distant in time than is the case with parallelism.  Convergence is thought to be due primarily to the independent species lines experiencing the same kinds of natural selection pressures.  Convergence is also referred to as convergent evolution.  Convergence results in homoplasies.
convergent evolution
see convergence.
core body temperature
the temperature of the internal organs in the chest cavity, abdominal region, and head in animals.  See hyperthermia and hypothermia.
core tool  click this icon to hear the preceding term pronounced
a tool made from a relatively large block of rock rather than from the flakes that are removed from it by percussion flaking in the manufacturing process.  Most hand axes are core tools.
cosmic radiation  click this icon to hear the preceding term pronounced
streams of highly penetrating charged particles (composed of free electrons, protons, alpha particles, and a few heavier atom nuclei) that bombard the earth at high speed from outer space.  On entering our  upper atmosphere, they commonly collide with gas atoms and alter the atomic structures of those atoms.
cranial capacity
the volume displaced by the brain within a cranium click this icon to hear the preceding term pronounced, or skull case.  Cranial capacity is a simple measure of brain size but not necessarily of intelligence.
creationism  click this icon to hear the preceding term pronounced
the belief that all species were created as they are today and that they have not undergone any evolution since then.  This view is usually based primarily on the Book of Genesis in the Judeo-Christian Bible.  Most creationists also believe that the Earth is very young (typically about 6,000 years old).  In the U.S. creationism is the basis for what has become known as "creation science."
Cro-Magnon  click this icon to hear the preceding term pronounced
the modern Homo sapiens who appeared in Europe by 40,000 years ago.  Their skeletons generally were lighter than the Neandertals who occupied Europe at that time.  The Cro-Magnon had broad, small faces with pointed chins and high foreheads.  They are the ancestors of modern Europeans.