page_title: Common descent
section_title: Potential objections
hierarchical_section_title: Common descent / Potential objections
context_page_description: Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. Its broadest application, the last universal common ancestor of all life on Earth, is a central assumption of modern evolutionary theory.
  Common descent is an effect of speciation, in which multiple species derive from a single ancestral population. The more recent the ancestral population two species have in common, the more closely are they related. The most recent common ancestor of all currently living organisms is the last universal ancestor, which lived about 3.9 billion years ago. The two earliest pieces of evidence for life on Earth are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.
caption: 2005 tree of life shows many horizontal gene transfers, implying multiple possible origins.