Question

According to the fossil evidence, modern humans (a) evolved from chimpanzees; (b) evolved on a lineage that split from other apes 6 million years ago or more; \((c)\) lack any known ancestors during the past few million years.

Short answer

Option (b) is correct; humans evolved on a lineage that split from other apes over 6 million years ago.

Step-by-step solution

Analyze Option (a)

The statement 'modern humans evolved from chimpanzees' suggests that humans directly descended from chimpanzees. According to evolutionary biology, humans and chimpanzees share a common ancestor, but humans did not evolve *from* chimpanzees directly. Therefore, this option is incorrect.

Analyze Option (b)

The statement 'modern humans evolved on a lineage that split from other apes 6 million years ago or more' aligns with the fossil and genetic evidence. Scientists have established that humans and other great apes share a common ancestor, and the lineage leading to modern humans diverged from this common ancestor approximately 6 to 7 million years ago. Hence, this option is correct.

Analyze Option (c)

The statement 'modern humans lack any known ancestors during the past few million years' is inaccurate. There is substantial fossil evidence documenting the evolution of hominins, including species such as Australopithecus and Homo habilis, leading up to modern Homo sapiens over the past few million years.

Key concepts

Fossil Evidence and Human Evolution

Fossil evidence plays a crucial role in our understanding of human evolution. It provides tangible links that connect modern humans to our prehistoric ancestors. Fossils are the preserved remains or traces of organisms from the past. Through fossils, scientists can study the physical and biological aspects of these ancient beings. This helps them piece together the evolutionary story.

Key discoveries include:

• Australopithecus afarensis: Famous for the skeleton nicknamed "Lucy," this species provides evidence of bipedalism—walking on two legs—one of the major adaptations in human evolution.
• Homo habilis: Known as the "handy man," this species is associated with early stone tools, marking a significant leap in cognitive and technical abilities.
• Neanderthals: Our close relatives show complex social behaviour and tool use, highlighting our shared ancestry.

These fossils, along with many others, display the gradual changes in anatomy and behavior over millions of years, illustrating the path from our ancient ancestors to modern Homo sapiens. Fossil evidence continues to be a vital part of studying hominin evolution, offering insights that are not only scientific but also deeply human, connecting us to our evolutionary journey.

The Concept of a Common Ancestor

The idea of a common ancestor is a key concept in understanding human evolution. This is the species from which two or more different species diverged through evolution.

For instance, humans and chimpanzees, our closest living relatives, share a common ancestor. This ancestral species existed around 6 to 7 million years ago.

Here’s how it works:

• Divergence: Over millions of years, isolated populations of our common ancestor evolved in different directions due to environmental pressures and genetic variations.
• Separate Lineages: These evolutionary changes resulted in the distinct species we see today, such as humans, chimpanzees, and other great apes.
• Shared Traits: Despite these differences, we share many traits with other apes, such as certain genetic markers and aspects of physical anatomy.

Understanding the role of a common ancestor helps clarify the evolutionary pathways that lead to humans and dispels myths like the idea that humans evolved directly from chimpanzees.

Tracing Hominin Evolution

Hominin evolution tracks the lineage that has led to modern humans. This evolutionary path marks a series of adaptations and changes over millions of years. Hominins refer specifically to the tribe of species that includes modern humans and our extinct ancestors.

Significant milestones in hominin evolution include:

• Bipedalism: The ability to walk upright on two feet is a hallmark of hominin evolution.
• Tool Use and Manufacture: Early hominins like Homo habilis started using tools, leading to advancements in technology and survival techniques.
• Brain Expansion: Over time, hominins experienced significant increases in brain size, supporting complex thought, language, and social structures.
• Species Diversification: Several hominin species evolved and co-existed, including Neanderthals and Denisovans, before Homo sapiens became the sole surviving species.

Each of these adaptations showcases the dynamic progress of hominin evolution, culminating in the emergence of our species, Homo sapiens. By studying hominin evolution, scientists gain valuable insights into what makes us uniquely human.