Question

Help please. Need someone to help confirm if my answer is correct? Will give medal. A molecule that can be used as a molecular clock has a neutral mutation rate of one mutation per 5 million years. How many years ago did two species share a common ancestor if the molecules found in these two species differ by a total of eight mutations?

1.5 million years
10 million years
20 million years ** is this correct **

Answer 1

1 mutation ever 5 years
so 2 mutations after 10 years
3 mutations after 15 years
8 mutations will be after \( \sf \underline{~40~}\) years

so none of your answers are correct.

Answer 2

The only other option was 40 million years and I got it wrong? So I am lost. Any ideas?

Answer 3

40 is the only logical answer...
8 mutations * 5 million years = 40 million years

Answer 4

If that's wrong for some reason... I'd go for 20

Answer 5

ok yeah that is what i was thinking too, thanks.

Answer 6

No problem :)

Answer 7

The answer was 20 million.

Answer 8

Hm that's odd
Are you sure it's 1 mutation every 5 million years and not 10?

Answer 9

Remember that the answer is 20 million because:
The total estimated time it took for both lineages (Species A and Species B) to evolve from a shared ancestor is 40 million years. Since both species had random mutations occurring at the same time, they both contribute equally to the total years of the evolution. Species A contributed half and Species B contributed the other half, so we will divide the total amount of time by two. By dividing the amount of time that separates these two species in half, we determine how long ago their lineages shared a common ancestor.

40 million total years of evolution / 2 species (or lineages) = 20 million years of evolution from a common ancestor.

Answer 10

@thomaster @marylou004