Common ancestor

Common Ancestor

A common ancestor refers to an individual from which two or more different species or groups of organisms have descended. In the context of evolutionary biology, the concept of a common ancestor is fundamental to understanding the relationships between different species and the process of evolution.

Overview

The idea of a common ancestor is central to the theory of evolution, which posits that all life on Earth shares a common origin. This concept is often illustrated using a "phylogenetic tree", which is a branching diagram showing the inferred evolutionary relationships among various biological species based upon similarities and differences in their physical or genetic characteristics.

Types of Common Ancestors

• Most Recent Common Ancestor (MRCA): This is the most recent individual from which all organisms in a group are directly descended. For example, the MRCA of all humans is often referred to as "Mitochondrial Eve" or "Y-chromosomal Adam".

• Last Universal Common Ancestor (LUCA): This is the most recent common ancestor of all current life on Earth. LUCA is thought to have lived approximately 3.5 to 3.8 billion years ago.

Importance in Evolutionary Biology

Understanding common ancestors helps scientists trace the evolutionary history of species. By studying fossils, genetic sequences, and morphological characteristics, researchers can infer the traits of common ancestors and how they have diverged over time.

Methods of Determining Common Ancestry

• Genetic Analysis: By comparing DNA sequences, scientists can estimate the time since two species shared a common ancestor.

• Comparative Anatomy: Examining similarities in the structure of different organisms can provide clues about their evolutionary relationships.

• Fossil Record: Fossils provide direct evidence of past life and can help identify common ancestors by showing transitional forms.

Examples

• The common ancestor of humans and chimpanzees is estimated to have lived about 5 to 7 million years ago.
• The common ancestor of all mammals is believed to have existed around 200 million years ago.

Also see

• Evolution
• Phylogenetics
• Speciation
• Cladistics
• Homology (biology)