Endogenous Retroviruses

The strongest molecular evidence for evolution.

What are ERVs?

  • Endogenous retroviruses (ERVs) are viruses that insert their genetic code into host DNA
  • When this happens in reproductive cells, the viral DNA can be passed to offspring
  • These inherited viral sequences are called Endogenous Retroviruses (ERVs)
  • ERVs make up about 8% of human DNA
  • Most ERVs are now broken and non-functional due to mutations

Why are ERVs Evidence?

1. ERV Insertions are Random:

  • Retroviruses can insert their DNA at nearly any location in the genome
  • The chance of the same virus inserting at the exact same spot in two unrelated species is effectively zero
  • Finding ERVs in the same locations across species indicates common ancestry

2. ERVs are Shared Across Species:

  • Humans and chimpanzees share over 100,000 ERVs in identical locations
  • Some ERVs are found in all primates at the same locations
  • More distantly related species share fewer ERVs, exactly as evolution predicts

3. ERV Mutations Match Evolutionary Trees:

  • ERVs accumulate random mutations over time
  • The pattern of mutations in shared ERVs perfectly matches known evolutionary relationships
  • Closer relatives have more similar ERV sequences

Objections

"ERVs could have been created by God for a purpose."

This doesn't explain why ERVs show clear signs of being broken viral sequences, or why their distribution and mutation patterns perfectly match evolutionary predictions.

"Viruses could have infected similar locations independently."

The probability of a virus inserting at exactly the same spot in multiple species is astronomically low. With over 100,000 shared ERVs between humans and chimps, independent insertion is mathematically impossible.

"ERVs could have spread horizontally between species."

Horizontal transfer cannot explain why ERV patterns perfectly match evolutionary trees, or why more closely related species share more similar ERV mutations.

Probability

Key Facts:

  1. Human genome size: ~3 billion base pairs
  2. Shared ERV insertions between humans and chimps: >200
  3. Not all genomic locations are suitable for insertion. Let's conservatively estimate that 1% of the genome is insertable.

Calculation:

  1. Probability of a single ERV inserting at a specific location:

    \[P(\text{insertion}) = \frac{1}{3 \times 10^9 \times 0.01} = \frac{1}{3 \times 10^7} \approx \frac{1}{30,000,000}\]

  2. Probability of the same ERV inserting at the same location in both species independently:

    \[P(\text{shared insertion}) = P(\text{insertion})^2 = \left(\frac{1}{30,000,000}\right)^2 \approx \frac{1}{900,000,000,000,000}\]

  3. Probability of 200 shared insertions occurring independently:

    \[P(\text{200 shared insertions}) = \left(\frac{1}{900,000,000,000,000}\right)^{200} \approx \frac{1}{10^{3000}}\]

Interpretation:

The probability of 200 shared ERV insertions occurring independently in humans and chimpanzees is astronomically small (

\(\frac{1}{10^{3000}}\)
). For comparison:

  • Number of atoms in the observable universe:
    \(~10^{80}\)
  • Probability of randomly selecting the same atom from the universe 37 times in a row:
    \(~\frac{1}{10^{2960}}\)

Thus, the probability of shared ERV insertions occurring by chance is even lower than this already unfathomable scenario.

Explanation:

The evolutionary model explains these shared insertions simply:

  1. ERVs inserted into the genome of a common ancestor.
  2. These insertions were inherited by both human and chimpanzee lineages.

Conclusion:

The mathematical improbability of shared ERV insertions occurring independently provides strong support for the evolutionary model of common ancestry between humans and chimpanzees.