Remember these images?
These are one of the few remaining uncontacted indigenous tribes left on Earth. They were spotted by planes who scour the Amazon to find where such tribes may be living, primarily with the intention of ensuring that they are left alone.
On first perusal, given the many horrible precedents that exist, especially in the Americas, for what happens when uncontacted tribes meet the modern world, that seems like a sensible policy.
Live and let live and all that.
For this tribe, as for similar tribes in the Andaman Islands, New Guinea and a few other pockets, life is an eternal Stone Age, with no inkling or conception of the huge and developed modern civilisations that surround them, threatening to engulf them.
I wonder about whether stranding people in pre-history is a good thing or not. Equally, this lot didn't seem to be very welcoming to outsiders.
But I also wonder if perhaps the entire human race are in fact the neolithic spear chuckers of the universe.
One of the great questions raised by astronomy and the vastnesses of the known universe it has uncovered for us is that of alien life. With so many opportunities for life to develop elsewhere in the universe, it is frankly unthinkable that this planet would be the sole example of a life-bearing planet.
So, in that case, if the universe teems with life, why hasn't it contacted us? There are a few possible answers: the lifeforms aren't conscious; they are way too far away to get in touch; the universe is huge and we're far out from the galactic centre and perhaps they haven't found us yet despite our radio waves and Voyager.
For leading physicist Stephen Hawking, there's no doubt life is out there. And in a new documentary, he explains why he thinks it might not be benevolent towards us.
"If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans," he explains.
Which brings me back to my moral conundrum.
We no longer enforce contact with civilisation upon Stone Age tribes because all our previous experience of doing so indicates that it is damaging, in terms of health, well-being, population size, and a number of other measures, to the indigenous peoples involved.
Without any example of a successful encounter between civilisation and such a tribe, we must assume that the reason why life in the universe has not contacted us is not actually because they fear us, but possibly because they fear what impact they would have on us.
Perhaps Earth is little more than a couple of straw huts, galactically speaking. Perhaps our solar system is nothing more than an empty corner of rainforest where no one goes.
In galactic terms, perhaps we are the spear chuckers.