---
abstract: 'The discovery of high redshift quasars represents a challenge to the origin of supermassive black holes. Here, two evolutionary scenarios are considered. The first one concerns massive black holes in the local universe, which in a large majority have been formed by the growth of seeds as their host galaxies are assembled in accordance with the hierarchical picture. In the second scenario, seeds with masses around 100-150 $M_\odot$ grow by accretion of gas forming a non-steady massive disk, whose existence is supported by the detection of huge amounts of gas and dust in high-z quasars. These models of non-steady self-gravitating disks explain quite well the observed ”Luminosity-Mass" relation of quasars at high-z, indicating also that these objects do not radiate at the so-called Eddington limit.'
title: |
    [**Supermassive Black Holes in the Early Universe**]{}\
    J.A. de Freitas Pacheco\
    Université de la Côte d’Azur\
    Observatoire de la Côte d’Azur - Laboratoire Lagrange\
    06304 Nice Cedex - France\
---

Introduction
============

The cosmological nature of quasars (QSOs) was established in the early sixties (Schmidt 1963). An immediate consequence of the implied large distances for these objects was the realization that QSOs were among the most powerful energy sources in the 