A basic teaching of the Bahá'í Faith is that all life is the creation of one God, knowledge of Whom comes from successive Teachers. Thus, all religion comes from the same source and has been progressive, in cycles of guidance dispensed according to the understanding and development of humanity in the time it was received. Bahá'u'lláh, Whom Bahá'ís believe to be the latest such Mouthpiece of God, is therefore neither the first nor the last in a long line of such Teachers.
The Cycle which began with Adam, however, is ended, and a new Cycle has begun--one which will last 500,000 years. There will be many dispensations within that cycle, roughly 1000 years apart. Further, there were cycles and dispensations before the Adamic Cycle, although no records of them remain.
When asked why no evidence is found of the Prophets that preceded Adam, or of the kings who lived in the days of those Prophets, Bahá'u'lláh answered this way:
"Know thou that the absence of any reference to them is no proof that they did not actually exist. That no records concerning them are now available should be attributed to their extreme remoteness, as well as to the vast changes which the earth hath undergone since their time.When I was in school fifty years ago, we were taught that civilization was only six or seven thousand years old. Since then, archeology has discovered ruins of truly amazing civilizations as old as 30-40,000 years! A stone ax found in Great Britain is older than the great flood which dug the English Channel and created islands out of what had been a northwestern European peninsula at the end of an ice age 460,000 years ago.
Moreover such forms and modes of writing as are now current amongst men were unknown to the generations that were before Adam. There was even a time when men were wholly ignorant of the art of writing, and had adopted a system entirely different from the one which they now use....Witness, therefore, how numerous and far-reaching have been the changes in language, speech, and writing [since] the days of Adam. How much greater must have been the changes before Him!
Our purpose in revealing these words is to show that the one true God hath, in His all-highest and transcendent station, ever been, and will everlastingly continue to be, exalted above the praise and conception of all else but Him. His creation hath ever existed, and the Manifestations of His Divine glory and the Day Springs of eternal holiness [such as Those for Whom we do have records: Adam, Abraham, Moses, Krishna, Buddha, Christ, Muhammad, Báb, & Bahá'u'lláh] have been sent down from time immemorial, and been commissioned to summon mankind to the one true God. That the names of some of them are forgotten and the records of their lives lost is to be attributed to the disturbances and changes that have overtaken the world." - Gleanings from the Writings of Baha'u'llah, p. 172-174
The past twenty years or so have revealed geological evidence of so many catastrophes--several that nearly wiped out humans--that it is a wonder we are here at all! Every day a new potential danger is discovered and reported to us via news media and social networks. Bahá'u'lláh, writing more than a century ago, commented:
"Mention hath been made in certain books of a deluge which caused all that existed on earth, historical records as well as other things, to be destroyed. Moreover, many cataclysms have occurred which have effaced the traces of many events. Furthermore, among existing historical records differences are to be found, and each of the various peoples of the world hath its own account of the age of the earth and of its history. Some trace their history as far back as eight thousand years, others as far as twelve thousand years....it is clear and evident how much the accounts given by the various books have differed." - Gleanings from the Writings of Baha'u'llah, p. 174Every day, humanity is learning new things, not only about our past, but also toward potential future. We now know that all people are a single species race and variety, for instance, which was not taught that way when I was a child.
My point is not that we should spend our days looking over our shoulders waiting for the next catastrophe--since we now know "The Big One" is coming for us sooner or later. Nor am I saying that the details of history are certain. What is clear, however, is that change is part of the process of life on this planet, and I find the Bahá'í Faith to be a useful tool in dealing with such an uncontrollable and often unpredictable reality.
The only control anyone has is in how to react to the changes and chances of this life. And the Bahá'í Teachings assure me that there is a Plan to Creation, plus, as religion has always done, comforts me that human life has a purpose.