Fossils suggest that the first major trait distinguishing hominins from other primates was
a. A larger brain.
b. Erect posture.
c. Forward-facing eyes with depth perception.
d. Tool making.

Verified step by step guidance

1. Understand the term 'hominins': Hominins refer to the group of species that includes modern humans, our immediate ancestors, and other extinct relatives that are more closely related to us than to chimpanzees.
2. Identify the key evolutionary traits of hominins: Traits such as bipedalism (walking on two legs), larger brain size, tool use, and other adaptations distinguish hominins from other primates.
3. Analyze the timeline of evolutionary traits: Fossil evidence suggests that bipedalism (erect posture) appeared early in hominin evolution, predating the development of larger brains, advanced tool use, and other traits.
4. Consider the role of bipedalism: Walking upright on two legs is a defining characteristic of hominins and is considered the first major trait that set them apart from other primates.
5. Review the other options: Larger brain size, tool making, and forward-facing eyes with depth perception are important traits, but they either appeared later in evolution or are shared with other primates, making bipedalism the most likely answer.

Key Concepts

Hominins

Hominins are a group of species that includes modern humans and our closest extinct relatives. They are characterized by traits that distinguish them from other primates, such as bipedalism and increased brain size. Understanding the evolutionary lineage of hominins is crucial for interpreting fossil evidence and identifying key traits that set them apart from other primates.

Bipedalism

Bipedalism refers to the ability to walk on two legs, which is a defining characteristic of hominins. This adaptation is believed to have evolved due to various environmental pressures, allowing early hominins to travel longer distances and free their hands for tool use. Fossil evidence, such as the structure of the pelvis and leg bones, provides insights into the evolution of bipedalism in hominins.

Cognitive Evolution

Cognitive evolution encompasses the development of advanced brain functions, including problem-solving, planning, and tool-making abilities. A larger brain relative to body size is often associated with increased cognitive capabilities. This concept is essential for understanding how hominins distinguished themselves from other primates, particularly in their ability to create and use tools, which played a significant role in their survival and adaptation.