[Lewis Thomson (OP)]

Paul is puzzled by this and looking for answers.

"I read that DNA genealogy companies only look at about 30% of ones DNA. Can they determine your Neanderthal percentage or would they not do that because it might be frowned upon in higher social circles? If they looked at all your DNA would it enable us to track our family trees further back? It's a pity gravestones are not marked with Q codes or something similar, enabling folk to establish links."

Can you help them? Leave your answers in the comments below...

[evan_au]

Direct-to-the public DNA testing services have improved dramatically over the years, as DNA sequencing technology has advanced exponentially.

Early tests were looking for "Single Nucleotide Polymorphisms" or "SNPs", where different variants exist in the population.
- And some of these SNPs come mainly from certain geographic areas
- Even by tracking a few hundred to a thousand of these base-pair variants (out of 3 billion nucleotides in human DNA), they could connect people to a parent population, and even connect lost relatives.
- This technique was used to catch the Golden State Killer
http://science.org/content/article/we-will-find-you-dna-search-used-nab-golden-state-killer-can-home-about-60-white
- It is thought that Neanderthal DNA makes up 1-5% of human DNA, so if they sampled several thousand SNPs, they could get a fair measure of your Neanderthal (or Denisoven) heritage

These days, the cost of full-genome sequencing has also reduced (but still much more expensive than testing SNPs), so we can expect that direct-to-the-public tests looking at more than 0.001% of human DNA will become available, but initially at a premium price.
- Eventually, we may get to the point where a full genome scan is done at birth (some people think this may prove an economic benefit for health care), but we are not there, yet
- In some ways, our ability to read DNA is advancing faster than our ability to extract useful health advice from it.