Step-by-step explanation:
Natural Instinct is always selfish. The question posed is rather an effortless one to answer and those who would advocate that humans are not naturally selfish are either misunderstanding the question or ignorant of evolution. Take a parent throwing themselves under a car to save their child, is that a selfless act? What about a firefighter who puts his life in risk every day to save lives or a soldier who mans a wall to hold an enemy at bay from harming those that the soldier has sworn to protect, are they acting selflessly?
Let us simply separate emotion from this and understand how natural instinct works. Natural instinct, evolution and natural selection are processes whereby the strongest genetic material remains and while we might attribute the aforementioned acts as selfless etc, what we need to recognize is that what drives us to do such things is not common sense or reason, it is a natural instinct to defend the genetic material, to protect the species which in itself is a deeply ingrained selfishness.
Even the firefighter and the soldier, who consider the needs of the position before taking their respective post, their choice to take those risks is a decision based on saving lives, of not personal selfishness but protecting the egocentric human species and ensuring it's survival.