Best way for creating a concrete class?

[Techno]

So I have a base class which has protected properties and also implements an interface.
The method in the interface, its signature has been changed in the base class to be abstract as I want the children/inheritors override/implement this method.


So now I will have a range of classes, lets call them:

Baby,
Toddler,
Child,
Teenager


All this inherit from "HumanBase", which implements an interface as explained above.

Now, I need to have some factory of some kind where it will return me the correct type of object but as an Interface i.e:

public IHuman Create(string stuff)
{
    // here create the concrete class and return it
}

so thats ok.

But here is the problem:

how would I set all the base properties etc... from the HumanBase from this factory type pattern? I know you can only access protected properties from the base class itself and also the children that inherit from the base class.
What I mean is, should each of the classes (baby, toddler etc...) have a constructor which takes in the parameters and then in the constructor let it set itself up?