Kill the CPL branch, kill the FORTRAN branch, save ALGOL, save Simula, save Lisp, save Forth, kill COBOL just to be sure. Scheme and CL come from Lisp.
Smalltalk comes from Simula+Lisp, influences Lisp and CLOS borns, Io and Self come from Smalltalk.
The ML branch comes out of nowhere, immediately suppress Caml, let SML evolve, Miranda, Haskell and Clean will come from that branch.
ABC and Python would never born without C and FORTRAN.
No FORTRAN means no BASIC, and GOTO considered harmful would never happen.
Having killed the CPL branch, Kernighan and Ritchie will never design C, meaning that Objective C, C++, C#, Java, JavaScript and all the C-like languages will never come to life. No C means no UNIX, no C++ means no Windows, no Objective C means no NeXTSTEP and no Mac OS.
Without the ubiquitous presence of UNIX and C, actually functioning Lisp/Forth systems would replace them.
No one would ever think of the existence of something like a ``personal computer'', computing would be a ``smart-people only'' sector, just like physics, the internet would be a simple network to just communicate.
Facebook and social networks would never born, since the whole ``lets ues a komputer fur errything :3'' thing would be shifted several years in the future, when:
1) With the absence of the internet, young generations would (hopefully) become smarter.
2) The entire world population would be more mature.
3) Without having to think of idiots that want to be 1337 h4x0r, security holes of misfunctioning profoundly defective by design systems like Windows and Unix derivatives, spending valuable time on useless things like social networks, PHP, Ruby on Rails and ``how to script ur kewl new websight'', and printers, computer scientist would had more time thinking on real problems, and probably computers would be more advanced (or maybe not, but at least there would be no x86).