The following was posted by David Vance in the ISOGG group in FaceBook today. As one of Ken’s acolytes back in the early days of Y-DNA Haplogroup I research, I feel compelled to post some links about his works. Ken helped guide me through testing of individual STRs and SNPs before autosomal testing was even available.
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The early pioneers in genetic genealogy in this group will remember Ken Nordtvedt, who I just heard passed away earlier this month at 86. His Wikipedia page (https://en.wikipedia.org/wiki/Kenneth_Nordtvedt) has already been updated.
While his contributions far exceeded genetic genealogy, in our field he was an early innovator in more accurate Y-DNA TMRCA algorithms back when most of us were still fan-girling over Bruce Walsh’s original 2001 paper on the subject. Ken’s Interclade TMRCA methodology is still the basis for the SAPP tool TMRCAs and have held up remarkably well over the decades.
But more than that, Ken was a major force in analysis and discovery in the I haplogroup for many years.
RIP and thank you to one of our departed visionaries and a giant upon whose shoulders we stand.
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See also https://genarchivist.net/showthread.php?tid=2028
Jim Robeson,
I1a-M253 > DF29 > CTS6364 > S4795 > S4767 > S4770 > Y13495/Y13016 > Y29634/S4774 > A13294 > FTA86767
Jims BBS 
Being a little slow, and not keeping up with the world, I only found out about Ken’s passing today. I was re-reading old emails from him, hoping to glean some missing tidbit of information that I may have overlooked back in the days when I still knew so little, not that I know much more two decades of research later..
I had actually started to draft an email to him when I decided to do a quick search to see what new information he may have published before I took up any of his time, only to find several articles regarding his passing, but everything mentioned his physics career and nothing, until I stumbled in here, mentioned his wonderful contributions to genetics and genetic genealogy. Like you, I learned about testing for individual STR’s and SNP’s, as one of the early identified PF49+ folks..
He will be greatly missed, and I am sorry I waited a decade to reach back out.
~Jim
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