# What happened to DNA from when we were reptiles **URL:** \ **Category:** Factual Questions\ **Created:** [November 2, 2005, 9:19pm UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174 "2005-11-02T21:19:47Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 2, 2005, 9:19pm UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/1 "2005-11-02T21:19:47Z")
Back when humans were reptiles what happened to our DNA that coded for things like scales or the ability to breath underwater? Did those DNA strands slowly transform into DNA that coded for different proteins (ie, the DNA that made scales a billion years ago transformed into the DNA that codes for keratin which we use to make fingernails as a guess) or did those DNA strands just stop being transcribed and over generations eventually mutated so badly that they are now junk DNA? ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [November 2, 2005, 9:39pm UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/2 "2005-11-02T21:39:14Z")
> [@Wesley Clark](#): > > Back when humans were reptiles what happened to our DNA that coded for things like scales or the ability to breath underwater? Did those DNA strands slowly transform into DNA that coded for different proteins (ie, the DNA that made scales a billion years ago transformed into the DNA that codes for keratin which we use to make fingernails as a guess) or did those DNA strands just stop being transcribed and over generations eventually mutated so badly that they are now junk DNA? Humans have no reptile ancestors, though both reptiles and humans have a common ancestor. As to the rest, I could make some half assed statements, but I will let someone who can give a succinct answer do it. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [November 2, 2005, 9:43pm UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/3 "2005-11-02T21:43:07Z")
> [@Wesley Clark](#): > > Back when humans were reptiles what happened to our DNA that coded for things like scales or the ability to breath underwater? Did those DNA strands slowly transform into DNA that coded for different proteins (ie, the DNA that made scales a billion years ago transformed into the DNA that codes for keratin which we use to make fingernails as a guess) or did those DNA strands just stop being transcribed and over generations eventually mutated so badly that they are now junk DNA? Both, as I understand it. Hair/fur is a modification of scales IIRC. I also read somewhere that we still have the genes for the superior sense of smell many animals have; it’s just inactive and highly corrupted from genetic drift. ---
**Author:** ![Ms2001](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ms2001/32/18463_2.png) [@Ms2001](https://boards.straightdope.com/u/Ms2001)\ **Post date:** [November 3, 2005, 2:09am UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/4 "2005-11-03T02:09:50Z")
> [@Wesley Clark](#): > > Back when humans were reptiles what happened to our DNA that coded for things like scales or the ability to breath underwater? Mine’s in my safe deposit box. Didn’t you keep yours? ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [November 3, 2005, 2:11am UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/5 "2005-11-03T02:11:59Z")
> [@Mr2001](#): > > Mine’s in my safe deposit box. Didn’t you keep yours? My mother threw mine out when I went to college. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 3, 2005, 2:35am UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/6 "2005-11-03T02:35:48Z")
> [@Mr2001](#): > > Mine’s in my safe deposit box. Didn’t you keep yours? My mom was too busy with her secret identity as wonderwoman to busy herself with something as pedestrian as saving my DNA. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 3, 2005, 3:51am UTC](https://boards.straightdope.com/t/what-happened-to-dna-from-when-we-were-reptiles/329174/7 "2005-11-03T03:51:11Z")
Generally important genes get converted to new functions over time through mutation and selection. We still have most of the same genes that our early tetrapod ancestors (loosely speaking, “reptiles”) had, they just function somewhat differently. Also, some genetic instructions can lay unexpressed for a very long time: it has been determined that [chickens still retain the ability to grow teeth](http://www.usc.edu/hsc/info/pr/hmm/00fall/benchmarks.html) (or at least rudiments of them) more than 60 million years since the last bird had them. Some very basic structural genes govern similar developmental processes in both insects and vertebrates, which have been separate for more than half a billion years.