other authors (Moorbath et al., 1973; Bridgwater et al., 1981) who would rather
assume these as inorganic structures or some unclear inclusions.
In the layers of the formations from the Warrawoona and Pilbara Groops
(West Australia) and Mushandike (Zimbabwe) aged 3.5 bln. years no imprints
of living forms have been detected. Only biogenic structures in stromatolytes
with an increased isotope ratio of ¹²C/¹³C have been found.
As most ancient authentic fossil microorganisms are considered the
findings from the Fig Tree Group in Swaziland, South Africa (see Table 5).
Well-preserved unicellular organisms defined as bacteria and blue-green
algae are well visible in the photographs (Fig. 1–10). Their more typical
representatives are Eubacterium isolatum (0.7 μm long) and
Archaeosphaeroides barbertonensis (17—20 μm in diameter). According to
the authors (Knoll and Barghoorn, 1977) a process of division is observed
in some of them. In the opinion of Schopf (1976) these spheric formations
are not bacteria but remains of prebiotic microsphere-like structures, similar
to those spontaneously formed upon mixing inorganic compounds in
laboratory conditions. The data, however, are more in favour of the
conception that living organisms have arisen prior to the Swaziland system.