Knowledge · Praktiker
Common Descent Explained Simply
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A bacterium, a fungus and a human seem utterly different. And yet they share the same code and the same deep root. All life belongs to a single, vast family tree.
What common descent means
Common descent means: all species trace back to shared ancestors. The further back you go in the tree, the closer the branches move together.
At the very bottom lies a single origin. This idea is the core of evolution and links the whole diversity of life.
The tree of life
We picture the relationships as a tree. Closely related species sit on neighboring branches, distant ones on widely separated limbs.
The human does not sit at the top but on one of millions of branches. Every branch has the same long history behind it.
Evidence from DNA
The strongest evidence lies in DNA. All living things use the same genetic code, the same four building blocks and similar core genes.
The more similar two species’ DNA, the closer their relationship. From these similarities, the tree of life can be reconstructed astonishingly precisely.
Evidence from fossils
Fossils show how forms changed over time. There are transitional forms that combine features of two groups.
So we find, for example, fish with the first leg buds or reptiles with feathers. Such finds fit exactly the branchings in the tree.
Why LUCA is the common origin
Trace all branches back and they meet in one population. This is called LUCA, the last universal common ancestor.
From there the path runs over billions of years and countless small steps. How these steps work is shown in mutation and variation.
Frequently asked questions
Did humans descend from apes?
Not directly. Humans and today's apes share a common ancestor. So we are relatives with a shared root, not descendants of today's apes.
What is LUCA?
LUCA stands for the last universal common ancestor of all life today. From this single population, all bacteria, plants and animals descend.
What does common descent mean exactly?
It means all species trace back to shared ancestors and ultimately to a single origin. All life thus forms one single, widely branching family tree.
How do we know all living things are related?
Mainly from DNA: all living things use the same genetic code and share many core genes. Fossils and transitional forms fit this and confirm the same relationships.
Was LUCA the very first life?
No. LUCA is the most recent ancestor that all life today shares. Before it there were probably even simpler life forms, but none of their direct descendants have survived to the present.
Are some species more highly evolved than others?
No. Every species alive today has had exactly the same length of evolution behind it. Bacteria are not „more primitive‟, just differently adapted to their environment than, say, mammals.
Sources and further reading
- Evidence for Evolution — National Geographic
- Tree of Life — Science
Update note (as of: 06/04/2026)
First publication of the common descent spoke.
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