Avi,
You asked,
"Do you believe this notion of Atlanteans being "20-60 feet tall"?"
--> Yes. Even the Bible says there were giants.
“There were giants in the earth in those days....” (Genesis 6:4)
“And there we saw the giants....” (Numbers 13:33)
“Which also were accounted giants....” (Deuteronomy 2:11)
“For only Og king of Bashan remained of the remnant of giants....” (Deuteronomy 3:11)
"Wouldn't we find fossiles of these species?"
--> According to Theosophy, we have. It has been said that bones of these giants have been found, and they have been passed off as dinosaur bones and animal bones.
"Aren't some of the dinosaur fossiles that we have found very old, so if such as species existed we would expect to find them as well?"
--> Dinosaur fossils have also been found.
Evidence exists today of these prehistoric giants.
“...we may turn to the scientific journals of 1858, which spoke of a sarcophagus of giants found that year on the site of that same city. As to the ancient pagan writers — we have the evidence of Philostratus, who speaks of a giant skeleton twenty-two cubits long, as well as of another of twelve cubits ... nevertheless, it was that of a giant, as well as that other one discovered by Messecrates of Stire, at Lemnos — ‘horrible to behold,’ according to Philostratus....” (Secret Doctrine vol 2 p 278)
“... the Abbe Pegues (cited in de Mirville's Pneumatologie) affirms in his curious work on ‘The Volcanoes of Greece’ that ‘in the neighbourhood of the volcanoes of the isle of Thera, giants with enormous skulls were found laid out under colossal stones....’ ” (Secret Doctrine vol 2 p 278)
“Certain excavations in America in mounds and in caves, have already yielded in isolated cases groups of skeletons of nine and twelve feet high. These belong to tribes of the early Fifth Race, now degenerated to an average size of between five and six feet. But we can easily believe that the Titans and Cyclopes of old really belonged to the Fourth (Atlantean) Race, and that all the subsequent legends and allegories found in the Hindu Puranas and the Greek Hesiod and Homer, were based on the hazy reminiscences of real Titans — men of a superhuman tremendous physical power....” (Secret Doctrine vol 2 p 293)
“It is at the entrance of some of these [viharas in Bamian] that five enormous statues, of what is regarded as Buddha, have been discovered or rather rediscovered in our century, as the famous Chinese traveller, Hiouen-Thsang, speaks of, and saw them, when he visited Bamian in the VIIth century.... The Buddhist Arhats and Ascetics found the five statues, and many more, now crumbled down to dust.... The largest is made to represent the First Race of mankind, its ethereal body being commemorated in hard, everlasting stone, for the instruction of future generations, as its remembrance would otherwise never have survived the Atlantean Deluge. The second — 120 feet high — represents the sweat-born; and the third — measuring 60 feet — immortalizes the race that fell, and thereby inaugurated the first physical race, born of father and mother, the last descendants of which are represented in the Statues found on Easter Isle; but they were only from 20 to 25 feet in stature at the epoch when Lemuria was submerged, after it had been nearly destroyed by volcanic fires. The Fourth Race was still smaller, though gigantic in comparison with our present Fifth Race, and the series culminated finally in the latter.... These are, then, the ‘Giants’ of antiquity, the ante- and post-diluvian Gibborim of the Bible. They lived and flourished one million rather than between three and four thousand years ago.” (Secret Doctrine vol 2 pp. 338-340)
The Bamian statues are the Afgan statues that were blown up by the Taliban. (The Taliban, along with everyone else, mistook these as statues of Buddhist origin.) They are
lifesize statues of the giants of that day.
Bamian Statues and Theosophy
Bamian
"The Bamian Statues: Their Mysterious Origin" by H. P. Blavatsky
The statues on Easter Island give a clue.
“The Easter Island relics are, for instance, the most astounding and eloquent memorials of the primeval giants. They are as grand as they are mysterious; and one has but to examine the heads of the colossal statues, that have remained unbroken on that island, to recognize in them at a glance the features of the type and character attributed to the Fourth Race giants.” (Secret Doctrine vol 2 p 224)
“Easter Island was ... taken possession of ... by some Atlanteans; who, having escaped from the cataclysm which befell their own land, settled on that remnant of Lemuria only to perish thereon, when destroyed in one day by its volcanic fires and lava.” (Secret Doctrine vol 2 p 326)
“...most of the gigantic statues discovered on Easter Island, a portion of an undeniably submerged continent — as also those found on the outskirts of Gobi, a region which had been submerged for untold ages — are all between 20 and 30 feet high. The statues found by Cook on Easter Island measured almost all twenty-seven feet in height, and eight feet across the shoulders.” (Secret Doctrine vol 2 p 331)
“The Easter Isles in ‘mid Pacific’ present the feature of the remaining peaks of the mountains of a submerged continent, for the reason that these peaks are thickly studded with Cyclopean statues, remnants of the civilization of a dense and cultivated people, who must have of necessity occupied a widely extended area.” (Secret Doctrine vol 1 p 322)
“ ‘Even at the date of Cook’s visit, some of the [Easter Island] statues, measuring 27 feet in height and eight across the shoulders were lying overthrown, while others still standing appeared much larger. One of the latter was so lofty that the shade was sufficient to shelter a party of thirty persons from the heat of the sun. The platforms on which these colossal images stood averaged from thirty to forty feet in length, twelve to sixteen broad. . . . all built of hewn stone in the Cyclopean style, very much like the walls of the Temple of Pachacamac, or the ruins of Tia-Huanuco in Peru.... THERE IS NO REASON TO BELIEVE THAT ANY OF THE STATUES HAVE BEEN BUILT UP, BIT BY BIT, BY SCAFFOLDING ERECTED AROUND THEM’ — adds the journal very suggestively — without explaining how they could be built otherwise, unless made by giants of the same size as the statues themselves.” (Secret Doctrine vol 2 p 337)
"Also you say "they were large enough and strong enough to build Stonehenge by hand, which makes sense to me". Why does this make sense to you ?"
--> Because it does.
"Why does this make sense to you ?"
--> Because I think it is entirely possible that Stonehenge was built by hand by giants. I see no reason to automatically reject such an idea.