When can babies start trying to talk???

My MIL claims my BIL said his first words at 2 months old. I said there was no way, I didn’t believe a child could comprehend enough to speak that early. My daughter is 4 months, and I feel like she is too young to talk. But I swear some days she is trying to! Yesterday alone I heard her say mama 3 times, I though well maybe it’s a coincidence and she’s just babbling those noises. Well just now we were watching word party and they are doing opposites saying “up, down, up, down” and she joined in and tried to say “up down.” If it wasn’t for hearing them say it with her I wouldn’t of thought anything of it and I’d assume it was just babble. Any thoughts???

I tried googling to see what it says about baby language and development but I just saw a lot about babies talking early. Most at 4 months saying their first word.

(While typing this she has said mama trying to get my attention) 😂😂😂