It is understood that Adam a.s. and Nooh a.s. lived about one thousand years. We do not know whether their communities lived as long as they did or not. However, since prophets are examples to their communities, it is probable that they lived as long as their prophets. As a matter of fact, our Prophet lived as long as the average lifespan of the community and died when he was 63 years old.
The view among scholars vary on Nooh a.s. ranging from 950 years to 1700 years.
Allaah says concerning the length of time that Nooh (peace be upon him) remained calling his people:
“and he stayed among them a thousand years less fifty years” [al-‘Ankaboot 29:14]
Regarding the height, we were giants who shrunk over time.
“Allaah created Adam and he was sixty cubits tall. Then He said, ‘Go and greet those angels and listen to how they greet you, for that will be your greeting and the greeting of your progeny.’ He said, ‘Al-salaamu ‘alaykum (Peace be upon you).’ They said, ‘Al-salaamu ‘alaykum wa rahmat-Allaah (Peace be upon you and the mercy of Allaah).’ So they added the words ‘wa rahmat Allaah.’ And everyone who enters Paradise will be in the form of Adam. People kept on growing smaller until now.”
Narrated by al-Bukhaari, 3336; Muslim, 7092
According to a version narrated by Muslim: “Everyone who enters Paradise will be in the form of Adam who was sixty cubits tall. People kept growing smaller until now.”
With regard to the words of the Prophet (peace and blessings of Allaah be upon him), “People kept growing smaller until now,” al-Haafiz ibn Hajar said in Fath al-Baari (6/367): “This means that in every generation people grew shorter than the previous generation, and continued to grow shorter until the time of this ummah, then they stayed like that.”
https://islamqa.info/en/20612
Regarding how old mankind is, there is nothing in Islam that defines the period between Adam and Muhammad (peace be upon them both); indeed the length of time that Adam (peace be upon him) lived is not known.
But there are some ahaadeeth and reports which, if we put them together, we can arriver at an approximate length of time, but that not cover the complete period.
10,000 years : The period between Adam and Nooh (peace be upon them both)
10,000 years : The period between Nooh and Ibraaheem (peace be upon them both)
unknown : The period between Ibrahim and Moosa (peace be upon them both)
1700 years : The period between Moosa and ‘Eesa (peace be upon them both)
600 years : The period between and ‘Eesa and Muhammad (peace be upon them both)
1400 years : age of Islam
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27,700 years
https://islamqa.info/en/20907
930 years : Life span of Adam a.s.
950 years : Life span of Nooh a.s.
195 years : Life span of Ibraaheem a.s.
125 years : Life span of Moosa a.s.
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1,200 years
http://www.eislamicarabic.com/prophets-ages.html
27,700 + 1,200 = 28,900
So by estimate, not counting the gaps, we could say humans have been around for about 29,000 years. 10 centuries as mentioned above is a long gap. If we were to assume the unknown gap above is less than or equal to 70 centuries then human age on earth can't be no more than 100,000 years and not 100s of thousands or millions as some think. Of course, only Allah knows the real numbers but if I were to put a number on it i would think that to be a ball park estimate.