Horses have a longer gestation period, 336 days compared to the human 266 days. That's a 70-day difference. Humans actually do a lot of physical development outside the womb, after birth, while horses, with their longer gestation, are essentially ready to go. At ten weeks, a human baby's neck muscles are strong enough to hold their head up for short periods, but if they were to get that extra maternal boost from an extended gestational period, it's possible they could be strong enough to hold their heads up all the time. Yes, during my horse quiz bowl years, I put entirely too much thought into this.