# Heliocentric Certainty Against a Bottleneck of Two?

**URL:** <https://discourse.peacefulscience.org/t/heliocentric-certainty-against-a-bottleneck-of-two/61>\
**Category:** Conversation\
**Tags:** Adam, Science, Featured\
**Created:** [December 29, 2017, 9:02pm UTC](https://discourse.peacefulscience.org/t/heliocentric-certainty-against-a-bottleneck-of-two/61 "2017-12-29T21:02:50Z")\
**Posts on this page:** 1\
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**Author:** ![swamidass](https://sea2.discourse-cdn.com/flex016/user_avatar/discourse.peacefulscience.org/swamidass/32/3_2.png) [@swamidass](https://discourse.peacefulscience.org/u/swamidass)\
**Post date:** [January 21, 2018, 11:04am UTC](https://discourse.peacefulscience.org/t/heliocentric-certainty-against-a-bottleneck-of-two/61/12 "2018-01-21T11:04:07Z")

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## Correctly Weighting Coalescents

I’ve been sure for a while that there was simplification introducing error into this estimate.

> [@swamidass](#):
>
> At the moment, all coalescents are weighted equally. This biases the averages to high recombination areas, which might be biased towards upward errors in TMRCA estimates. It would be wiser to average weighting by the length of the DNA segment to which the phylogeny applies.

I finally got around to correcting this part of the code, and recomputing the TMR4A. Here is what we arrive at, a TMR4A of 495 kya, nearly 500 kya. This is a better estimate.

 ![image](https://us1.discourse-cdn.com/flex016/uploads/peacefulscience/original/1X/94c9420257f170b3e5f847aff3363ba3451568a2.png)

## How Much Faster for a TMR4A of 100 kya or 6 kya?

How much faster would we have to see mutation to find a TMR4A a much lower level? These numbers change with this improved estimate.

1. If TMR4A was at 100 kya, we would expect the mutation rate to be 2.6e-8 per generation, or 5x more than observed.

2. If TMR4A was at 6 kya, we would expect the mutation rate to be 43e-8 per generation, or 83x more than observed.

That is why most scientists are going to find a single couple genetic origin of humans before 500 kya implausible. It just does not fit the evidence.

* * *

As I get more opportunities to refine the results, I’ll continue making them and posting them here.

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