Two critical steps in the evolution of humans were the :

Options

A. Evolution of bipedalism and enlargement of brain
B. making and using of tools
C. Exhibiting cultures and having sophisticated tools
D. Using fire and making shelters

Answer

**Step-by-Step Text Solution:**

1. **Understanding Human Evolution**: Human evolution is a complex process that involves various stages and species. It starts from early primates and progresses through several hominid species leading to modern humans (Homo sapiens).

2. **Identifying Key Ancestors**: The evolution of humans includes several critical ancestors such as:
- Dryopithecus
- Ramapithecus
- Australopithecus
- Homo habilis
- Homo erectus
- Homo sapiens

3. **Recognizing Critical Steps**: Among the many changes that occurred during human evolution, two critical steps stand out:
- **Bipedal Locomotion**: This refers to the ability to walk on two feet. Early ancestors used four limbs for locomotion, while modern humans (Homo sapiens) walk upright on two legs.
- **Increase in Brain Capacity**: Over time, there has been a significant increase in brain size. For instance:
- Australopithecus had a brain capacity of about 500 cc.
- Homo habilis had a brain capacity ranging from 650 to 800 cc.
- Homo erectus had a brain capacity of about 900 cc.
- Homo sapiens have a brain capacity of approximately 1450 cc.

4. **Conclusion**: The two critical steps in the evolution of humans are:
- The evolution of bipedalism (walking on two feet).
- The enlargement of brain capacity (increased brain size).

5. **Final Answer**: Therefore, the answer to the question is the evolution of bipedalism and the enlargement of brain capacity.

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