What's the biggest, most intelligent Machine we know now?
It's none other than the HUMANS, i.e., us.
If we consider humans as machines as I have considered, we can see our life is just like a Model which is trained by different trainers in different situations.
We are Natural Intelligence like we say AI.
Like Neural networks mimic human brain simulations, we ourselves are mimicking other people's works.
Considering our birth, a baby actually mimics its parents and the people around it.
The parents and other people just train the baby by showing them actions, and saying some words to repeat, which we can them as the datasets.
Another dataset is the walking stage of babies. They analyse how other humans actually walks i.e., with two legs, and will try to walk like that, accuracy won't be exact at first as they will fall. But as they get trained to walk, accuracy will become high.
If our ancestors walked on 4 legs, we could be doing the same. Someone in past got inspired to walk on 2 may be from nature itself and hence the present day we are doing.
The next stage is off schooling, the trainers are teachers and friends who train us with datasets of Knowledge, life, love, and character. Also, we can consider the TV/Celebrity Idols as some kind of trainer who provides a dataset of styles, attitudes, and fantasies.
Stage 4 is self-thinking, self-learning, and creating. This is not yet so evolved in AI, but we can hope it could be in the future. We, Humans, learned to take our decisions, and create and discover many scientific, moral, and social things. Even AI was created in this stage.
Coming to reinforcement learning, it's what we know, the appreciation we get is what makes us do things better. In humans, it can be a solid prize and emotional comfort. A student works more when he finds a teacher appreciates him well and so he can get more appreciation he desired. Between two people love happens because it's a mutually rewarding situation. That's emotional comfort.

We know the layers of processing in Deep learning, we are having that too. For taking a decision we go through several possibilities and filter out those until the final decision comes. When we are stuck somewhere, we got to take an extra weight like asking someone else close to us to take the decision.
Basically, We can consider ourselves as machines or an Intelligence created by nature and nature being the head of the trainers.
Consider a small hoax, we humans and Earth are just advanced creation of some other species made for a entertainment to watch for them and they trained us using machine learning.

Some terms:
Dataset = a set of data or information that is used to feed to a machine for that to analyse it and process on the basis of it.
Layers : Layers in terms of computer science, In each layer some kind of filtering or process happens and gives the output to next layer.