Many attempts have been made to uniquely distinguish humans from the other animals. Use of tools was a promising one until we observed birds and monkeys using stones and sticks as basic tools for getting into shells and ants' nests. Speech also showed promise until monkeys learnt significant vocabularies in sign language. Farming - but no, ants farm fungus in their nests. Even burying our dead is no longer seen as a uniquely human trait. So, what action makes humans significantly different?
I suggest the fundamental difference is a human tendency to plant trees. Yes, planting trees - but not just as a crop or for the fruit and wood they might produce. All animals need to do things to provide food and shelter. Humans can and do grow things to harvest for food and shelter. But planting a tree is much more.
Squirrels harvest nuts and hide them and ants collect seeds and store them in larders. If these nuts and seeds are forgotten or otherwise left alone long enough in the dark and damp they may germinate but this isn't really planting a tree. Birds and insects are vitally important in the whole fertilisation business, but that isn't planting a tree.
When a human plants a tree, it cannot help but be a symbolic gesture. You must be aware of the scale of time and that you are making a gesture towards a promised future. It is a gesture of hope. You must be aware that the planting is to benefit those who come after you: your family; your children or grandchildren; your neighbours; the other animals of your environment. Humans have the ability to foresee and plan for their future even beyond their own death. We have a need for acts of faith, acts of renewal, ritual confirmations of continuity that is met uniquely in tree planting.
Even planting fruit trees is so much more of a symbolic act than farming annual crops like wheat or rice. You may fully intend to consume the produce from that tree, but not until some point in the future. A future at least years away, that you have imagined, that you have hoped for and believe you can bring about. A future of peace and justice enough for you and your children to enjoy the fruits of your labour. A future that may include quiet contemplation while sitting under the shade and in the comfort of the developing crown. A future in harmony with nature and bees doing their 'thing'. A future that may even include tree houses or at least the excitement and drama of tree climbing. A future that you are actively bringing into existence.
How right and proper it is that trees are planted in our civic places to symbolise remembrance, or nationhood, or bonds between cities and nations, or peace. Trees are an analog for peace and for most humans the planting of a tree is one of the most hopeful things anyone can do.
But every planting of a tree symbolises these things. It is the planting of such symbols that sets us apart.
If you have not planted a tree and looked into the future then you don't know what it is to be truly human.