Final answer:
The correct completion for the sentence is option b. 'Inexorably and smoothly', as human evolution was a gradual process. Humans evolved anatomically and intellectually, with Homo sapiens emerging around 300,000 years ago. The 'out of Africa' and 'multiregional evolution' models offer two frameworks for understanding this process.
Step-by-step explanation:
Every evolutionary step had to build successively on every preceding one so that, inexorably and smoothly, fully evolved modern humans could emerge in Africa about 100,000 years ago. The correct phrase to complete the sentence based on the evolutionary process would be option b. Inexorably and smoothly. This indicates a gradual and persistent progression in human evolution without suggesting any sudden changes or emotional aspects to the process.
Modern humans, known as Homo sapiens, evolved through a process marked by a series of developments both anatomically and intellectually. Fossil evidence suggests Homo sapiens emerged in a form biologically identical to present-day humankind around 300,000 years ago, with the oldest known specimen discovered in Morocco in 2017.
There are two primary models that explain this evolutionary process: the "out of Africa" model and the multiregional evolution model. The "out of Africa" model is the most commonly accepted and suggests that modern humans first appeared in Africa and then expanded out, spreading across the globe. In contrast, the multiregional evolution model proposes that Homo sapiens evolved simultaneously in various regions from Homo erectus. While these models have different hypotheses, they aren't necessarily exclusive, and the most accurate representation of human evolution may involve a combination of both theories.