I saw an article in the news recently about a study that suggested that life existed on Earth 300 million years earlier than we previously thought, which was during the late heavy bombardment. Could life actually have arisen under those conditions? Or does this suggest some external source of life, such as a meteorite?

I haven't had a chance to read the original paper in full and I don't think it is open access but,  you should be able to read the summary at least at
http://www.pnas.org/content/early/2015/ … 2.abstract

There is also a short press piece about it here
http://www.sciencealert.com/life-on-ear … e-suggests

At present I don't think anyone is suggesting that this new dating implies an extra-terrestrial source for life. It could perhaps mean that we are wrong about just how inhospitable the planet was at this earlier point, but this is just speculation on my part.

thanks and having had a quick read of the paper - spot on that exactly what the paper is saying. That does not of course exclude the possibility of life being carried to earth on a meteor!