There are narrations stating that Muhammad taught that Adam was created 60 cubits (90 feet) tall, and that people have been diminishing in size from Adam's time:
Sahih al-Bukhari 3326
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 Muslim 2841
Abu Huraira reported Allah's Messenger (ﷺ) as saying:
Allah, the Exalted and Glorious, created Adam in His image with His length of sixty cubits, and as He created him He told him to greet that group, and that was a party of angels sitting there, and listen to the response that they give him, for it would form his greeting and that of his offspring. He then went away and said: Peace be upon you! They (the angels) said: May there be peace upon you and the Mercy of Allah, and they made an addition of "Mercy of Allah". So he who would get into Paradise would get in the form of Adam, his length being sixty cubits, then the people who followed him continued to diminish in size up to this day.
The fact that Adam was 90 feet tall is also taught in Sahih al-Bukhari 3327, 6227, and Sahih Muslim 2834c-d.
Of course, if Adam were 90 feet tall, then Eve would also need to be similarly sized. And, it is anatomically impossible for a 70 or 80 foot tall woman to give birth to a modern-sized human baby, so all of their kids would have been gigantic as well.
The narration also states that people have been continuing to decrease in stature from the time of Adam. Fath al-Bari, as quoted by Islam Q&A, says of this narration:
Fath al-Bari 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.
This would indicate that there were 80, then 70, 60, 50... 20 foot tall people or people groups, in the early days of humanity, at least. Such would have required giant houses, clothing, tools, and food sources. No remains of any such gigantic civilization - let alone a skeleton of a person from such a civilization - have ever been found.
Scientifically, the largest known bipedal organisms were nowhere near 90 feet tall. Issues involving circulation, and skeletal structure manifest long before 90 feet of height, which is why all of the tallest dinosaurs were quadrupeds. So, if a human being were this large, their mere existence would seem to be a miracle, if one wants to maintain that the laws of physics have remained constant in the universe since the time of Adam.
Some Muslims, in response, have stated that the Hadith only talks about Adam's size in Heaven, and that when he was sent to earth his size was reduced, and as a result, the end should be read as something like, "people have continued to be smaller in stature since Adam's time".
Firstly, this would be an assertion that the Muslim translators of Sahih al-Bukhari and Sahih Muslim were completely mistaken in their rendering of the passage, which would need to be demonstrated. Machine translations agree with how they are rendered above:
Likewise, Fath al-Bari, as quoted above, understood this to be saying that humanity has continued to decrease in stature, not that it has "stayed small since Adam's time".
Secondly, this revised rendering seems to go against the context of the passage. If the passage were rendered in this way, one would expect a mention of Adam's size decreasing - something like, "Adam was created 60 cubits tall, then his size decreased, and people have continued to be small since then". However, none of the narrations mention Adam's size decreasing when he came to earth. Rather, he is merely said to have been 60 cubits tall.
Therefore, this response not only depends on a difficult or non-standard translation of the last part of the narration, but also on an insertion of an implied "(and then he was reduced in size)" into the text of the Hadith. These factors make this response unlikely to be true.
Sometimes, Westernized Muslims will present Islam as being compatible with modern Evolutionary theory, despite the account of the special creation of Adam given in Surah 15:26-33 and 38:71-72. This article demonstrates that if a Muslim were to try to use Evolution to refute Christianity, they will have refuted Islam much more. Not only does the Quran describe the special creation of Adam, but Islamic tradition holds that Adam was gigantic, which would be rejected out of hand by any modern Evolutionary biologist.
Furthermore, Islam's account of Adam's tremendous size creates many other scientific, historical, and archaeological difficulties for Islam.