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the process of producing milk through the mammary glands; a feature seen only in mammals.
Lamarck, Jean-Baptiste de
(1744-1829) one of the first people to study the relationships between organisms and propose the theory of evolution; most noted for his work on the "Great Chain of Being," a lineage classification system that suggested organisms might be ranked according to their morphological complexity with humans being the highest. He proposed the idea that morphology changed as a result of the organism's attempt to fit into its environment (i.e., that a giraffe's long neck is the result of the animal stretching to reach higher branches). These newly acquired morphological features would be passed along to subsequent generations.
the inheritance of acquired characters.
cranial suture that articulates between the parietals and occipital bones in the cranium.
land bridge
an area of land that connects two continents or larger areas of land; can be partially or temporarily submerged.
late childhood
considered to be between the ages of 6 and 12 years.
a relative term used to describe features that are farther from the midline or center of the body; the opposite of medial.
a supercontinent present in the northern hemisphere during the Paleozic era that collided with Gondwana to form Pangea; consisted of present day North America and Europe.
lesser apes
the gibbon and siamang.

a Middle Paleolithic stone tool manufacture technique in which a core is carefully prepared by removing flakes from around its periphery, with the final removal of a large flake from the core. This large flake can be used as a tool with sometimes only minimal retouch.

life expectancy
the average age an organism is expected to live.
life history
what an organism goes through and its developments from conception until death.
the descendants or ancestors of an individual or family.
a relative term referring to the part of the mouth that is closer to the tongue; the opposite of buccal.
Linnaeus, Carolus
(1707-1778) a Swedish biologists who saw all life forms as unchanging; authored Systema Naturae, and in its tenth edition (1758) proposed a method for organizing taxa that became the basis for all later taxonomic classification; also proposed the use of binomial nomenclature for naming taxa; some of his more significant contributions include the naming of humans as Homo sapiens and classifying the genus Homo with other primates. Unlike the "Great Chain of Being," which was a linear classification, the Systema Naturae organized animals in a two dimensional nested hierarchy according to morphological similarities, with humans no longer the highest order.
[Greek: "stone"] a stone tool or any byproducts of stone tool production (i.e., debitage).
living floor
a surface found during excavations that is characterized by a relatively higher number of artifacts that could be associated with human occupation.
place; location

movement to or from a place by an organism. Forms of locomotion include bipedalism, knuckle walking, brachiation, swimming, flying, etc.

Lower Paleolithic

[syn. Lower Stone Age] the time period of tool manufacture approximately dated between 2.5 million years and 250,000 years; tools associated with this time period include those of the Oldowan and Acheulean technologies.


the nickname for specimen number AL 288-1; a female Australopithecus afarensis discovered in 1974 at the Hadar formation in Ethiopia that approximately dates to 3.2 million years. Characterized by evidence for bipedalism, Lucy is the most famous and complete Australopithecine fossil ever recovered. Lucy received her nickname from a the Beatles' song "Lucy in the Sky with Diamonds".

the section of the back between the thorax and the pelvis.
lumbar curvature
the anteriorly convex curvature of the spine in the region of the lumbar vertebrae; helps to distribute the weight of the upper body more efficiently and brings the center of gravity closer to the midline and above the feet.
lumbar vertebrae
refers to the vertebrae that are located between the thoracic vertebrae and the sacrum.
Lyell, Charles
(1797-1875) a Scottish geologist who authored Principles of Geology (1830) in which he proposed the "Principle of Uniformitarianism" that states that natural laws are constant, that the geological processes seen today acted the same in the past, that geologic change is slow and happens at a uniform rate, and that the earth is fundamentally the same today as it was in the past. Lyell's ideas were influential for many other scientists, including Charles Darwin.