Final answer:
The term that best describes how early humans solved problems for survival and improvement in their lives is D) Natural selection, which is the process of organisms better adapting to their environment leading to evolutionary changes over generations.
Step-by-step explanation:
The term that best describes the process where early humans solved problems to ensure survival and improvement in their lives is D) Natural selection. Natural selection is a process where organisms better adapted to their environment tend to survive and reproduce more successfully. This concept, often referred to as "survival of the fittest", was developed independently by both Alfred Russel Wallace and Charles Darwin. It is the fundamental mechanism by which evolutionary changes take place over generations, leading to adaptations that enhance an organism's chances of survival and reproduction.
Adaptation is a crucial aspect of natural selection where organisms exhibit traits that are a "fit" to their environment, allowing them to thrive under given conditions. Over time, these adaptive traits become more common in the population due to the successful survival and replication of the individuals that possess them. Natural selection has molded everything in the biological world, including the early humans who had to constantly adapt to their changing environments to survive.