Summary
All living things descend from shared ancestors, evidenced by universal DNA and genetic code.
In depth
Evidence includes shared genetic code, similar biochemistry (ATP, DNA), homologous structures, vestigial organs and DNA similarity (humans and chimpanzees share about 98.8 percent of comparable sequence). Nested patterns of similarity allow a tree of life to be built.
Genes such as those for cytochrome c are conserved across kingdoms.
The tree of life is supported by independent evidence that agrees. Genes in different species correspond (orthologues), and the order of genes along chromosomes is often conserved; human chromosome 2 is a fusion of two ape chromosomes, with telomere sequences in the middle and a second inactive centromere. Pseudogenes such as the broken vitamin C gene in primates are shared with the same errors.
Embryology gives further clues: vertebrate embryos have pharyngeal arches, and whales develop hind limb buds. Biogeography fits too: island species resemble those of nearby mainlands.
Remember: common ancestry does not mean that humans came from modern chimpanzees; humans and chimps share a common ancestor that lived about 6 to 7 million years ago.
Frequently asked questions
What is Common Ancestry?
All living things descend from shared ancestors, evidenced by universal DNA and genetic code.
Which area of biology covers Common Ancestry, and how advanced is it?
Common Ancestry is one of the 53 topics in Evolution. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Homologous Structures, Molecular Clock, Vestigial Structures.
Can you give an example of Common Ancestry?
Pseudogenes shared by humans and other primates, such as the broken vitamin C gene, point to common ancestors.
What should I learn before Common Ancestry?
Common Ancestry is a Beginner topic, so no earlier topic is required. Other Beginner topics in Evolution that pair well with it include Evolution, Natural Selection, Charles Darwin.
What topics are related to Common Ancestry?
The closest topics to Common Ancestry are Homologous Structures, Molecular Clock, Vestigial Structures, Divergent Evolution. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Common Ancestry?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Common Ancestry. To practise the whole of Evolution, use the Evolution quiz.
How is Common Ancestry different from Homologous Structures?
Common Ancestry: All living things descend from shared ancestors, evidenced by universal DNA and genetic code. Homologous Structures: Body parts with similar structure from a common ancestor but different functions, like a human arm and bat wing. Read both side by side and note what each one explains.
How should I study Common Ancestry step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Homologous Structures and explain the difference aloud. Finally, take the Evolution quiz and come back to this page for any question you miss.