I just often wonder how much more scientific evidence we actually need to understand this.

LOL, apparently infinite. One part of our human connection is that we are such social animals that we really ignore our own inner knowing much of the time and "go along to get along." We take queues from each other about what is real, and filter out everything we were taught growing up is not supposed to be real. Yet I think it is intuitive for a child to recognize their connection to all life. They experience connection, are easily delighted, and have a baseline state of love and joy even if they sometimes flow into anger or sadness. Everything else is taught.