Human Origins and Evolution - Core Concepts

Vocabulary flashcards covering key terms from the lecture notes on human origins, evolution, and related concepts.

Sahelanthropus tchadensis

Earliest known hominin (~7 million years old) discovered in Chad; chimp-sized brain with hominin brow ridges, indicating an early split from the chimp–human lineage.

Hominins

Members of the lineage that leads to humans after the split from the common ancestor with chimps; includes Sahelanthropus, Ardipithecus, Australopithecus, and Homo.

Ardipithecus ramidus (Ardi)

Early hominin, bipedal on land but quadrupedal in trees; dated about 4.4 million years ago.

Lucy (Australopithecus afarensis)

Fossil showing clear evidence of upright walking; dated about 3.2 million years ago.

Australopithecus afarensis

Hominin species that includes Lucy; among early bipeds in Africa.

Bipedalism

Walking on two legs; a defining feature that emerged in hominins during the last 5–7 million years.

Foramen magnum

Hole at the base of the skull where the spinal cord enters; its more central position in humans reflects an upright posture.

Homo ergaster

Early African Homo species; ancestor to later Homo lineages; central to discussions of Out-of-Africa vs. multiregional models.

Homo sapiens

Modern humans; the species that evolved from earlier Homo lineages.

Multiregional hypothesis

Idea that modern humans evolved in parallel from Homo ergaster populations around the Old World with some gene flow between populations.

Out-of-Africa hypothesis

Idea that modern humans originated in Africa about 200,000 years ago and then spread, replacing other hominins; supported by mtDNA and Y-chromosome data.

mtDNA

Mitochondrial DNA; maternally inherited genetic material used to trace lineage and test human origins.

Y-chromosome DNA

Paternal lineage DNA used to test human origins; corroborates mtDNA findings for Out-of-Africa.

Cann et al. study

Pioneering mtDNA study that supported the Out-of-Africa origin of modern humans.

Neanderthals

Extinct hominins that lived in Europe and western Asia from about 600,000 to 30,000 years ago; coexisted with modern humans.

MRCA of humans and chimpanzees

Most recent common ancestor of humans and chimps, dating roughly 5–7 million years ago.

Neoteny in humans

Retention of juvenile features in adults; proposed as part of the differences between humans and chimpanzees.

Fossil footprints in Tanzania (3.5 mya)

Evidence of upright posture in early hominins, indicating derived bipedalism.

Three sources of phylogenetic information

The fossil record, molecular DNA sequences, and anatomy; used to resolve evolutionary relationships.