Origin: A Genetic History of the Americas

The microblades were struck off of cores, small rocks that
had been carefully flaked in order to yield blades of a consistent
size and shape. Burins, carefully shaped stones, were probably
used in the preparation of these microblade compound tools.
End scrapers were fashioned by removing flakes from one end
of a core. The sharpened surface may have had a variety of
uses, including processing hides from animals and shaping
antler, bone, or wooden tools. Bifaces, or stone knives, axes, or
points flaked in such a way as to produce two sides, were
common components of many different kinds of toolkits,
including microblade assemblages.
Toolmakers prepared numerous cores (microcores) in
advance, possibly when staying at encampments such as Swan
Point CZ4b. They would then carry these cores with them as
they traveled, ensuring that they had the ability to make tools
even when far away from the sources of good-quality stone. If
their spearpoints were damaged in the course of hunting, it
would have been relatively easy and economical to replace lost
or broken microblades by flaking them off of their pre-prepared
cores and fitting them into the bone projectile point. A skilled
toolmaker could certainly replace projectile points created out of
a single piece of stone, but it would have been more time
consuming, more costly in terms of raw materials, and more
cumbersome to carry around the larger cores required to make
bifacial projectile points than microblades.
Microblades appear at sites in interior Alaska for over 10,000
years, indicating their success as an adaptation. But they
weren’t a static technology; we know from the archaeological
record that people made these tools in at least two major ways.
Toolmakers using the Yubetsu method prepared a bifacially
flaked, leaf-shaped blank. They would then strike the biface
along its top ridge to create a flat platform and carefully shape
the angle of one end. Then they removed tiny flakes from one