Human Origins and Brain Evolution

Human Origins and Larger Brains

• Hominids diverged from ape lineage at least 5 million years ago.
• Significant brain and body expansion occurred in past 2 million years.
• Early hominid ancestor was likely Australopithecus.
• Homo habilis and Homo erectus evolved from Australopithecus.
• Modern humans (Homo sapiens) appeared 200,000-100,000 years ago.
• Brain evolution spurred by environmental factors, adaptability, complex social patterns, physiological changes, and neoteny.
• Human brain structure similar to other animals (e.g., rats), but larger due to more neurons.
• Wide variations in human body size, brain size, and intelligence.
• Human behavior is largely culturally learned, not inherent.

Comparative Research in Neuropsychology

• Comparative investigations aim to:
  • Understand brain mechanisms.
  • Create animal models for human neurological disorders.
  • Describe brain evolutionary development.

Genes, Environment, and Behavior

• Humans inherit one allele of each gene from each parent.
  • Alleles can be homozygous (same) or heterozygous (different).
• Alleles can be:
  • Dominant (expressed as a trait).
  • Recessive (not expressed).
  • Codominant (both expressed).
• Wild-type allele is most common in a population.
  • Other alleles are mutations.
• Mutations can alter DNA sequences, often negatively affecting nervous system structure and behavior.
• Selective breeding is a form of genetic manipulation.
• Genetic engineering alters an animal's genome.
  • Clones have identical genetic composition to parent/sibling.
  • Transgenic animals contain new/altered genes.
  • Knockout animals lack a specific gene.
• Genotype influences phenotype but the environment through epigenetic mechanisms also plays a role, influencing gene expression without altering the code.