The colossal black holes at the centres of galaxies probably formed shortly after the Big Bang, a study suggests.
Some of these behemoths are billions of times more massive than our Sun.
Supercomputer simulations indicate the conditions for the birth and growth of these giants could have been set in play by the merger of galaxies when the cosmos was just a few hundred million years old.
The research, by Lucio Mayer and colleagues, is published in Nature.
The teams modelling found that the collision and union of two massive young galaxies could produce an enormous disc of rotating gas, and that this disc could become unstable and fall in on itself to make a truly colossal star tens of thousands of times more massive than our Sun.
When this star then collapses to form a black hole, it is big enough to go on consuming gas at the rate needed to achieve the supermassive sizes recognised to exist in the early Universe through to the present day.
Enormous black holes are thought to lie at the centres of most large galaxies. Understanding how they came into being and how they evolved is a major question in astrophysics.
There is an amazing correlation between black holes and their galaxies, observed Professor Marta Volonteri from the University of Michigan.
Every time you look in a galaxy for a [supermassive] black hole, you find it; and the mass of the black hole is typically a 1,000 times less than the mass of the galaxy.
How has such a great correlation been established? How is it possible they knew so well about each other throughout these past 13 billion years? So we really want to know how the black holes started and how they grew with time, she told BBC News.
Professor Volonteri was not part of the team which did the modelling but the originator of the theory tested by Professor Mayer at the University of Zurich.
Mayers group said the new research challenged the idea that galaxies grew in a hierarchical fashion - in small steps that sees gravity pull small masses together to form progressively larger structures.
Our result shows that big structures - both galaxies and massive black holes - build up quickly in the history of the Universe, said co-worker Dr Stelios Kazantzidis from Ohio State University.
If that is the case, it has important consequences.
For example, the standard idea, that a galaxys properties and the mass of its central black hole grow in parallel, will have to be revised, Dr Kazantzidis said.
In our model, the black hole grows much faster than the galaxy. So it could be that the black hole is not regulated at all by the growth of the galaxy. It could be that the galaxy is regulated by the growth of the black hole.
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