Territorial behavioural adaptation is exactly what cinematic MRI reveal when used to view a pregnant woman womb. Twin fighting in the womb does not stated today, it has started for long time ago but it is now that evidence about it is out. Cinematic MRI reveals the footage of twin fighting in the womb. The video is everywhere now on the internet should if you care to view the video.
In the cinematic MRI footage, it shows the legs of the smaller of the two foetuses extending into the space of the larger foetus, as if trying to push it back or kick at it, this is a kinkd of territorial behaviour we learnt in our biology, although we’re not sure of exactly what is going on between the foetuses.