Final answer:
The out-of-Africa hypothesis suggests that Homo neanderthalensis, Homo floresiensis, and Homo erectus likely went 1. extinct due to competition, environmental challenges, and interbreeding with Homo sapiens.
Step-by-step explanation:
Out-of-Africa Hypothesis and Extinction of Homo Species
In light of the out-of-Africa hypothesis, a parsimonious reason why species like Homo neanderthalensis, Homo floresiensis, and Homo erectus do not exist today could be a combination of several factors. The most supported theories suggest that these species went extinct due to a range of factors including competition with Homo sapiens, inability to adapt to changing environments, and possible interbreeding leading to genetic dilution, rather than evolving into different species. Specifically, Homo neanderthalensis likely faced extinction due to a combination of climate change, competition for resources with Homo sapiens, smaller population sizes, and reduced genetic diversity. Genetic evidence further supports some level of interbreeding between Homo sapiens and Homo neanderthalensis, meaning their genetic material has not entirely disappeared but rather became part of the Homo sapiens genetic pool.
Homo erectus and Homo floresiensis also faced challenges that led to their decline. For Homo erectus, they had a widespread migration pattern but eventually went extinct possibly due to environmental pressures and competition. Homo floresiensis, on the other hand, might have been a result of isolated evolution with limited resources leading to extinction. The notion that these species migrated and evolved into different species is less supported in light of genetic findings and fossil evidence that suggest replacement rather than continuous evolution into modern humans.