Answer:
Alliances contributed to the start of World War I because so many alliances were being created all over the world. Most alliances would agree to protect one another if either country in that alliance got attacked by other countries. So if a country got attacked by another one, you could expect the country being attacked to be backed up by their alliance, creating future wars to commence.
Hope this helps.
Just a couple things
diseases that affect them during pregnancy
birthing troubles
possibly cultural or religious traditions that would make it hard for them to survive.
