From Fossils to Humans: Evolution & Human Variation
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Assignment2EXAMPLE-Summer2026.docx
Part 1: Hominin Evolution Timeline
1. Species #1
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
Image of
Species #1
2. Species #2
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
Image of
Species #2
3. Species #3
Image of
Species #3
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
Image of
Species #4
4. Species #4
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
5. Species #5
Image of
Species #5
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
6. Species #6
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
Image of
Species #6
7. Species #7
Image of
Species #7
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
4. Species #8
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
Image of
Species #8
1. Species #1
· When they lived
Image of
Species #9
9. Species #9
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
10. Species #10
· When they lived
· Where they lived
· Physical characteristics
· Culture/tools
Image of
Species #10
Part 2: Evolution & Human Variation
Human evolution shows a clear pattern of change over time, and these changes help explain why humans today display such a wide range of variation. When looking at a timeline of hominins, one of the most important early changes is the development of bipedalism, or the ability to walk on two legs. Early species like Australopithecus afarensis had small brains but showed clear adaptations for upright walking. Over time, later species such as Homo habilis and Homo erectus began to show increases in brain size along with more advanced tool use. This trend continued until modern Homo sapiens, who developed large, complex brains and sophisticated cultural behaviors. Overall, the timeline shows a gradual shift from small-bodied, small-brained primates to highly adaptable humans with advanced technology and social systems (Shook et al., 2023; Smithsonian Institution, n.d.).
These changes were shaped by evolutionary forces such as natural selection, environmental pressures, and adaptation. For example, as environments became more variable, individuals who were better able to solve problems, use tools, and communicate were more likely to survive and reproduce. This helped increase brain size over time. Similarly, bipedalism may have been advantageous because it allowed early hominins to move more efficiently and free their hands for carrying objects or using tools. Evolution does not happen in a straight line, but rather as a process of adaptation to changing conditions, which explains why different hominin species developed different traits depending on their environments (Shook et al., 2023).
These evolutionary processes also help explain variation in modern humans. One clear example is skin color. Human populations that remained near the equator were exposed to high levels of ultraviolet (UV) radiation, which led to the evolution of darker skin with more melanin to help protect against UV damage. In contrast, populations that migrated to regions with lower UV exposure evolved lighter skin, which allows the body to produce enough vitamin D from limited sunlight. This shows how physical traits are shaped by environmental conditions rather than fixed or universal characteristics (BioInteractive, n.d.).
Understanding evolution also helps explain why humans are not divided into clear biological “races.” Modern biological anthropology shows that human variation is continuous, meaning traits change gradually across geographic regions rather than forming distinct groups. Most genetic variation exists within populations rather than between them, meaning humans are far more similar than different. Because of this, the concept of biological race does not accurately represent human diversity and is better understood as a social concept rather than a biological one (Shook et al., 2023; Science Insights, 2026).
In conclusion, the study of human evolution shows that variation in modern humans is the result of long-term processes such as natural selection, migration, and adaptation to different environments. The hominin timeline demonstrates how these changes occurred over millions of years, while modern human traits reflect those same evolutionary patterns. By understanding evolution, we can better understand both human diversity and the shared biological history that connects all people.
Works Cited
BioInteractive. (n.d.). The biology of skin color. https://www.biointeractive.org/sites/default/files/SkinColor-Educator-film.pdf
Science Insights. (2026). Biological race in anthropology: What science says. https://scienceinsights.org/biological-race-in-anthropology-what-science-says/
Shook, B., Braff, L., Nelson, K., & Aguilera, K. (2023). Explorations: An open invitation to
biological anthropology (2nd ed.). https://pressbooks.calstate.edu/explorationsbioanth2/
Smithsonian Institution. (n.d.). Brains. https://humanorigins.si.edu/human-characteristics/brains
