Question

A revolution in the study of human evolution is under way due to the invention of techniques that enable DNA sequencing not only of modern humans but also of ancient humans (introduced in Chapter 20 ). Modern humans (Homo sapiens) and archaic humans called Neanderthals (H. neanderthalensis) shared a common ancestor in Africa but diverged in different geographic areas. When modern humans migrated out of Africa and dispersed around the world starting about 70,000 years ago, they overlapped with Neanderthals in Europe. This scenario is best described as: a. Species living in sympatry following allopatric speciation b. Species living in sympatry following sympatric speciation c. Species living in allopatry following allopatric speciation d. Species living in allopatry following sympatric speciation

Short answer

The correct answer is a. Species living in sympatry following allopatric speciation.

Step-by-step solution

Understand the terms

First, let's define the terms: 1. Sympatry: When two or more species coexist in the same geographic area. 2. Allopatry: When two or more species are separated by a geographical barrier and do not come into contact. 3. Allopatric speciation: The formation of new species due to geographic isolation. 4. Sympatric speciation: The formation of new species within a shared geographic area due to other factors, such as a change in behavior or habitat preference.

Evaluate the scenario of modern humans and Neanderthals

According to the given scenario, modern humans (Homo sapiens) and Neanderthals (H. neanderthalensis) shared a common ancestor in Africa but diverged in different geographic areas. When modern humans migrated out of Africa and dispersed around the world starting about 70,000 years ago, they overlapped with Neanderthals in Europe.

Choose the best suitable term

Now, let's analyze the options: a. Species living in sympatry following allopatric speciation b. Species living in sympatry following sympatric speciation c. Species living in allopatry following allopatric speciation d. Species living in allopatry following sympatric speciation In this scenario: - Modern humans and Neanderthals diverged in different geographic areas, so allopatric speciation took place. - When modern humans migrated out of Africa and spread around the world, they overlapped with Neanderthals in Europe, meaning they coexisted in the same geographic area. So, they were living in sympatry. Considering these points, the best suitable term is: a. Species living in sympatry following allopatric speciation

Key concepts

DNA Sequencing in Human Evolution

The advent of DNA sequencing technology has revolutionized our understanding of human evolution. Through the analysis of genetic material, both from modern and ancient humans, scientists are able to map out ancestral lineages and interactions between different human species.

For instance, by comparing the genomes of modern humans, Homo sapiens, with those of Neanderthals, a picture of our shared history emerges. It is revealed that these two species, once thought to be separate branches, actually interbred. The evidence of this lies in the DNA of non-African modern humans, who carry small percentages of Neanderthal genetic material.

As a critical tool in the study of evolution, DNA sequencing allows us to trace back the migration patterns, survival strategies, and even health-related predispositions of our ancestors, presenting a fascinating, molecular-level narrative of human history.

Allopatric Speciation

Allopatric speciation is a fundamental mechanism by which new species arise. It occurs when a population is divided by a geographic barrier, such as mountains, oceans, or vast distances, leading to genetic isolation.

Over time, due to the different selective pressures in the separate environments and the genetic drift, these isolated populations undergo evolutionary changes that can lead to the development of distinct species.

Evolutionary Processes Involved

• Natural selection may favor different traits in different environments.
• Genetic mutations can occur randomly and, if they confer an advantage, may become more common in that isolated population.
• Genetic drift can cause gene frequencies to change at random, leading to divergence from the original population.

In essence, allopatric speciation lays the groundwork for the biological diversity seen across the globe.

Sympatric Coexistence

Sympatric coexistence refers to the phenomenon where two or more species share the same geographic space without being geographically separated. Unlike allopatric speciation, where isolation promotes divergent evolution, sympatric species must find ways to coexist without interbreeding.

This can be achieved through a variety of mechanisms, such as temporal separation, where species may be active or reproduce at different times, or ecological separation, where they occupy different niches within the same environment.

Examples in Nature

• Tree-dwelling insects that exploit different parts of the same tree.
• Birds that nest in the same area but feed in different territories or at different times.

Understanding sympatric coexistence helps to unravel the complex interactions and adaptive strategies that allow for biodiversity within shared habitats.

Human Migration out of Africa

Human migration out of Africa is a pivotal chapter in the story of our species. According to paleoanthropological research, Homo sapiens began dispersing out of Africa approximately 70,000 years ago, an event that shaped the genetic diversity of modern human populations.

This migration led to Homo sapiens encountering and sometimes interbreeding with other hominin species, such as Neanderthals in Europe, and Denisovans in Asia.

Impact on Human Evolution

• Genetic admixture introduced new genes into the Homo sapiens gene pool.
• Confrontation with new environments led to adaptations in skin color, immunity, and metabolism.
• Cultural exchange and technological innovation as humans adapted to diverse habitats.

Such migrations and subsequent interactions are more than mere footnotes in history; they are testament to the adaptability and resilience of human beings in the ever-changing tableau of Earth's geography.