Human Ancestry and Molecular Evolution

Vocabulary flashcards covering human ancestry, hominin species, molecular evolution, and genetic adaptations from Chapter 16.

Hominoid

The broadest primate category that includes both present and past greater and lesser apes: gibbons, orangutans, gorillas, chimpanzees, and humans.

Hominid

A primate classification including all modern and extinct great ape and human lineages, excluding lesser apes.

Hominin

The most recent and narrow primate lineage specific to Homo sapiens and their relatives, characterized by bipedalism.

Australopithecus

A bipedal hominin (sometimes referred to as Lucy) that lived in Africa about $2$ to $4$ million years ago, stood $4$ to $5$ feet tall, had human-like teeth, a gorilla-sized brain, and lived a hunter-gatherer lifestyle.

SRGAP2 gene

A gene first appearing in Australopithecus that is important for neuronal differentiation and allowed an increase in critical thinking skills.

Homo habilis

The oldest known species of Homo, dating to about $2$ to $3$ million years ago; a human-like cave dweller and the first to use tools extensively.

Homo erectus

A hominin living about $1$ million years ago with a shallow forehead, massive brow, and brain about one-third the size of modern humans; demonstrated social cooperation, use of fire, and male-to-female pairings.

Homo neanderthals

A hominin lineage that split from modern humans about $516{,}000$ years ago in Europe, possessing larger brains, prominent brow arches, muscular jaws, and large barrel-shaped chests.

MCR1 gene

A gene present in Neanderthals and some modern humans that is responsible for freckles, pale skin, and reddish hair.

Denisova hominin

A hominin discovered in $2010$ whose mitochondrial DNA proved distinct from Neanderthals and modern humans, showing evidence of red hair and interbreeding with modern humans around $40{,}000$ years ago.

Cro Magnum

The earliest known Homo sapiens fossils, discovered in a French cave in the late 1800s, showing evidence of culture, communal graves, jewelry, and intricate cave art.

Homo sapiens

Also called the 'wise human'; the only surviving species of Homo, which first appeared about $200{,}000$ years ago.

Molecular Evolution

An area of biology that studies evolutionary structural changes at the level of DNA and the genome.

Molecular Clock

A method using mutation rates in DNA to estimate the time two species have evolved independently, assuming an average rate of one base change per $25$ million years.

Chromosome 2

A chromosome unique to humans formed by the fusion of two ancestral chromosomes (present as 2a and 2b in chimpanzees), reducing the human chromosome count to $46$ compared to $48$ in chimps.

Hox genes

Homeobox genes that turn on in developmental sequence to pattern body regions; their expansion and duplication throughout evolution drove animal diversity.

Cytochrome c

A mitochondrial respiratory chain protein found in all eukaryotes, in which $20$ of the $104$ amino acids are completely conserved across eukaryotes, and whose sequence is identical between humans and chimpanzees.

Mitochondrial DNA

Maternally inherited genetic material with a higher mutation rate than nuclear DNA due to nearby reactive oxygen species, used to trace matrilineal ancestry.

Haplogroup

A genetic cluster of individuals sharing a common ancestor along a maternal line (via mitochondrial DNA) or paternal line (via the Y chromosome), often tracking geographic movements.

Genetic Admixture

The mixing of DNA that occurs when two genetically distinct populations interbreed, frequently following migration events.

Out of Africa theory

The model proposing that Homo sapiens evolved from Homo erectus within Africa and migrated out approximately $50{,}000$ years ago, subsequently interbreeding with other hominins and populating Eurasia.

Keratin gene mutation

A nonsense mutation that stopped widespread body hair in humans, allowing increased sweating and improved endurance migration in warm climates.

FOXP2 gene

A gene involved in human brain development, language, and speech that differs by two amino acids from the homologous protein in other mammals.

The field of biology that investigates evolutionary relationships and structural alterations at the level of DNA, genomes, and proteins is called _______.

Molecular evolution

Techniques in molecular evolution track lineage divergence by comparing genetic markers such as single nucleotide polymorphisms (SNPs), copy number variants (CNVs), and _______.

Short tandem repeats (STRs)

When comparing DNA sequences between two species, finding fewer base differences indicates a more _______ evolutionary divergence from their common ancestor.

Recent

Comparing protein sequences reveals that the eukaryotic mitochondrial respiratory chain protein _______ is $100\%$ identical in its amino acid sequence between humans and chimpanzees.

Cytochrome c

Cytogeneticists compare the microscopic _______ of chromosomes between primates to evaluate homology, noting a $99\%$ similarity between human and chimpanzee X chromosomes.

Banding patterns

Because it is inherited exclusively through the mother and has a high mutation rate caused by reactive oxygen species, _______ is used to trace matrilineal ancestry.

Mitochondrial DNA (mtDNA)

Paternal lineage and male migration patterns are tracked using non-recombining genetic markers passed directly from father to son on the _______.

Y chromosome

As Homo sapiens migrated across Eurasia, interbreeding with Neanderthals and Denisovans introduced archaic DNA into modern populations through _______.

Genetic admixture

During the last ice age, early human populations migrated from Siberia into North America across the land-exposed _______.

Bering Strait

At the molecular level, humans and chimpanzees share approximately _______ of their protein-encoding gene sequences.

$$98.7\%$$

Cortical and cerebellar development necessary for motor pattern coordination during bipedal walking is linked to the _______ gene.

AHI1 gene