The Bible is silent regarding the height of Adam. This may seem like a strange topic for a question, but there are some who speculate that Adam and Eve were actually created much taller than the average human today. According to one theory, Adam and Eve were about 15 feet tall.
Theories of a super-size Adam start with the fact that people before the flood lived extraordinarily long lives (Adam lived to be 930 years old, according to Genesis 5:5). There’s also the assumption that Adam was created with superior intellect. Through the centuries after the fall, humanity has decreased in longevity, in intellect, and—by extrapolation—in height.
The presence of very large animals and insects in the fossil record lends support to the theory that Adam was very tall. In 1940, the fossilized wing of Meganeuropsis americana was unearthed in Oklahoma. This dragonfly-like insect had a wingspan of almost two and a half feet (Harvard Magazine, Nov-Dec 2007, “DRAGONfly,” www.harvardmagazine.com, accessed 5/20/20). In 2020, fossils of giant turtles were found in northern South America: the shell of Stupendemys geographicus measures nearly nine and a half feet long, about 100 times the size of its nearest living relative (The Washington Post, Feb 13, 2020, “Turtles the Size of a Car Once Roamed the Earth. Scientists Just Found Their Fossils,” Reis Thebault, www.washingtonpost.com/science, accessed 5/20/20). Those who conjecture that Adam was taller than modern man reason that, if the animals were extra big in “prehistoric” times, why not humans?
Another bit of “evidence” suggesting that Adam was of great height is the mention of “giants” in the Bible: the Amorites of Canaan, the Rephaim, and Goliath the Philistine, for example. When encountering the people of Canaan, the majority of the Israelite spies claimed that “the land we explored devours those living in it. All the people we saw there are of great size” (Numbers 13:32). Amos states how the Amorites were tall in stature, hyperbolically comparing them to tall cedar trees (Amos 2:9). A Rephaite, King Og of Bashan, who opposed the Israelites in Moses’ time, is also described as a giant in the Bible, having a bed that was “more than nine cubits long and four cubits wide” (Deuteronomy 3:11). If the bed matched his stature, then Og could have been around 13 feet tall. Furthermore, Goliath is described as being six cubits and a span, which is over nine feet in height (1 Samuel 17:4). Could the great stature of these historical characters be a residual effect of Adam’s genetics? Some say “yes.”
There is also the occurrence of gigantism in humans. Robert Wadlow was measured at 8 ft, 11.1 in. before his death in 1940 (“The Tallest Man Ever,” www.guinnessworldrecords.com, accessed 5/20/20). It is doubtful, however, that people like Wadlow are proof that Adam was as tall: modern gigantism is a physical disorder, and individuals who grow to excessive heights almost always struggle with heart and circulatory problems.
The idea that Adam was a giant finds support in Islam, as well, although the Islamic tradition takes an extreme view. In the hadith, Abu Huraira relates that “the Prophet said, ‘Allah created Adam, making him 60 cubits tall’” (Sahih al-Bukhari, Book 55, Hadith 543). This would make Adam about 90 feet tall.
Despite making some intriguing claims, the theory that Adam and Eve were giants has no biblical evidence to support it. We have no hint in Scripture of how tall Adam was. There have been historical instances of people growing very tall, but to use those anomalies to propose a specific height for Adam is unwarranted. And extrapolating the average height of man based on the size of extinct insects and reptiles involves a similar amount of conjecture.