“Why did the chicken cross the road?”/“To get to the other side” is a classic riddle from the 19th century. “Y did the chicken X the road” is a math/science version.
   
“Y did the chicken X the road? To exchange genes”—Y chromosome and X chromosome?—was posted on Twitter by Jason Stockwell on July 2, 2015.
   
“Y did the chicken X the road? Solve for Y” was posted on Reddit—3amjokes on October 2, 2020.
     
       
Twitter
Kevin Bland
@kevbland
RT @BRIANGITTINS1 Y did the chicken x the road, then come back again, cross again, come back, cross, back, cross & then back again? No head
7:18 AM · Sep 17, 2009·Twitter Web Client
   
Twitter
Jason Stockwell
@dvm_uvm
Y did the chicken X the road? To exchange genes. #LCREU students sci translate #habitat #fragmentation #ECHOVT #UVM
2:40 PM · Jul 2, 2015·Twitter for iPhone
   
Twitter
morgan bryan
@morgbryan
Replying to @JimShockey_
Y did the chicken x the road? Cause Shockley was on the other side…
8:35 PM · May 19, 2017·Twitter for iPhone
 
Reddit—3amjokes
Posted by u/Castor_Deus October 2, 2020
Y did the chicken X the road?
Solve for Y
COMMENTS
WPRV
To Z herself home
     
Twitter
3AM
@3AM_Jokes
Y did the chicken X the road?... Solve for Y
5:16 AM · Oct 2, 2020·IFTTT
 
Twitter
wildprotons
@wildprotons
Y did the chicken X the road?
Solve for Y
4:13 PM · Oct 2, 2020·Twitter for iPhone