In the last couple of decades, our understanding of genetics has grown dramatically, providing overwhelming evidence that humans share common ancestors with all life on earth. Here are some of the main types of genetic evidence for common ancestry.

1. Genetic Diversity. Human children inherit 3 billion base pairs of DNA from each parent, but they are not an exact duplicate. The rate of change has been measured precisely to an average of 70 bases (out of our 6 billion total) per generation. So as we go back on the family tree, there are more and more genetic differences between us and our ancestors. For example, there would be about 140 differences between your DNA and that of your four grandparents, and 210 differences between you and your eight great-grandparents, and so on. That enables us to make a prediction from the amount of genetic diversity between two species about the time since their common ancestor population lived. Using non-genetic evidence, the common ancestor between humans and chimpanzees was estimated to have lived about 6 million years ago. The calculation from genetic differences gives a figure remarkably close to the estimated value.

2. Genetic “scars”. Just as scars stay on our bodies as reminders of past events, the DNA code contains “scars” and these are passed on from generation to generation. DNA scars result from the deletion or insertion of a block of bases (not just single base changes as in the previous section). Because we have a lot of these (hundreds of thousands) and they can be precisely located, they serve as a historical record of species. If we have the same scar as chimpanzees and orangutans, then the deletion or insertion must have occurred before these species diverged into separate populations. If we and chimpanzees have a certain scar but orangutans do not, we can conclude the deletion or insertion must have occurred after the common ancestor of chimps and humans separated from our common ancestor with orangutans. In this way we can create a detailed family tree of common ancestors.

3. Genetic synonyms. In a certain context, the words “round” and “circular” mean the same thing to an English speaker—they are synonyms. So too, there are “synonyms” in the genetic code—different sequences of DNA bases that mean the same thing to cells (that is, they cause the production of the same proteins). Mutations in the genetic code are often harmful, resulting in an organism not being able to successfully reproduce. But if the mutation results in a “synonym”, the organism would function the same and continue passing on its genes. Because of this we would expect the synonymous changes to be passed on much more effectively than non-synonymous changes. That is exactly what we find among the DNA of humans and chimpanzees: there are many more synonymous differences between the two species than non-synonymous ones. This is exactly what we would expect if the two species had a common ancestor, and so it provides further evidence that humans and chimpanzees were created through common descent from a single ancestral species.

The more research that is done on DNA, the more evidence we find that all life is related.

Further Reading

  • Evolution Basics: From Primate to Human, Part 1

    | Dennis Venema
    Blog Post
    Evolution Basics: From Primate to Human, Part 1 | Dennis Venema

    For many years, it was unclear if humans were more closely related to chimpanzees or to gorillas, but full genome sequences allowed us to resolve the issue. Read More >

    Basics PART 36 of 50
  • Evolution Basics: Genomes as Ancient Texts, Part 1

    | Dennis Venema
    Blog Post
    Evolution Basics: Genomes as Ancient Texts, Part 1 | Dennis Venema

    …while errors made by human scribes tend preserve a meaning of some kind...DNA replicating enzymes do not check to see if meaning (i.e. function) is preserved as they copy. Read More >

    Basics PART 15 of 50
  • Evolution and the Imago Dei Essays

    Evolution and the Imago Dei Essays

    You will find essays, poetry, art, and fiction in this special issue of the Image journal on the interactions between faith and science, with a special nod to evolution. Some may ask,... Read More >


Learn More

Blog series: Evolution Basics
By Dennis Venema
Written by BioLogos Fellow of Biology Dennis Venema, this series of posts is intended as a basic introduction to the science of evolution for non-specialists.
Blog series: The Evolutionary Origins of Genetic Information
By Stephen Freeland
Join astrobiologist Stephen Freeland for a look into the nature of information and the origins of life on earth. (These posts were originally published as a paper in the ASA?s academic journal, PSCF, and are reprinted here with permission.)
Blog series: Understanding Evolution: the Evolutionary Origins of Irreducible Complexity
By Dennis Venema
One of the challenges for discussing evolution within evangelical Christian circles is that there is widespread confusion about how evolution actually works. In this installment, we examine evidence that proteins in irreducibly complex (IC) systems can form and refine new interactions through gradual mechanisms.
Blog article: Where is the Genetic Evidence for Evolution?
By Kelsey Luoma
The discovery of DNA has revolutionized our understanding of common descent, particularly in the past few decades. Mutated genes spread through populations over generations, leading to evolutionary change. In this podcast, we look at several examples of genetic evidence for evolution.
Mark Noll, Francis A. McAnaney Professor of History, University of Notre Dame

BioLogos continues to show that firm belief in the truth-telling character of Scripture can support, rather than undermine, the best scientific investigations. All who are invested in any aspect of these questions should applaud their good work in transforming science and religion from a war zone to an instructive conversation.

- Mark Noll, Francis A. McAnaney Professor of History, University of Notre Dame
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