The hadith say humans were created in the physical image of Allah. Thus they began as tall as 90ft giants (60 cubits is the equivalent of 90 feet), and have been decreasing in height ever since. The oldest human remains found in Ethiopia (Lucy and Ardi) were actually shorter in height than us, thus Archaeological science has disproved this belief.
Narrated Abu Huraira:
The Prophet (ﷺ) said, “Allah created Adam, making him 60 cubits tall. When He created him, He said to him, “Go and greet that group of angels, and listen to their reply, for it will be your greeting (salutation) and the greeting (salutations of your offspring.” So, Adam said (to the angels), As-Salamu Alaikum (i.e. Peace be upon you). The angels said, “As-salamu Alaika wa Rahmatu-l-lahi” (i.e. Peace and Allah’s Mercy be upon you). Thus the angels added to Adam’s salutation the expression, ‘Wa Rahmatu-l-lahi,’ Any person who will enter Paradise will resemble Adam (in appearance and figure). People have been decreasing in stature since Adam’s creation.
Sahih al-Bukhari 3326
Vol. 4, Book 55, Hadith 543