What does "random" mean in this paragraph?

I was a i translate a book about how to dating for a males customer (sorry because this topic can offend you). But my customer is very picky, so i must translate very correctly. Now i has a paragraph as follows:
" Both femininity and masculinity refer to the appearance of the biological differences that exist between our two sexes; females can bear and feed children but at the cost of being physically more vulnerable. The terms refer to the biological characteristic of a male and a female and not just traits that have traditionally been seen as appropriate for males and females for random reasons."
What does "random" mean in this paragraph? I've searched on http://www.oxfordlearnersdictionaries.com/ and i see 2 meaning:
1. done, chosen, etc. without somebody deciding in advance what is going to happen, or without any regular pattern
2. (especially of a person) not known or not identified
The word "random" in this paragraph has 2st meaning, right? Can you help me to understand it? Thank you!