> - XPath literally didn't exist when CSS selectors were introduced

[citation required]

https://www.w3.org/TR/1999/REC-xpath-19991116/

https://www.w3.org/TR/REC-CSS1-961217

> W3C Recommendation 17 Dec 1996, revised 11 Jan 1999

There are various drafts and statuses, so it's always open to hair-splitting but based only on the publication date CSS does appear to win