Natural Resources, 2013, 4, 383-386
http://dx.doi.org/10.4236/nr.2013.45047 Published Online September 2013 (http://www.scirp.org/journal/nr)
383
Sexual Reproduction One Billion Years Ago
Petr N. Kolosov
Diamond and Precious Metal Geology Institute Siberian Branch, Russian Academy of Sciences, Yakutsk, Russia.
Received December 7th, 2012; revised June 9th, 2013; accepted July 11th, 2013
Copyright © 2013 Petr N. Kolosov. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The facts regarding to the early stages of algae evolution in the Precambrian are very rare (more than 542 million years
ago). In this paper, the author describes the first discovered evidence that the sexual reproduction process took place
one billion years ago. As it is known, sexual reproduction led to the diversity of living organisms on the Earth, and in
general, accelerated the evolution process.
Keywords: Microorganisms; Cyanobacteria; Algae; Cells; Sexual Reproduction; Evolution; Neoproterozoic; Siberia
1. Introduction
A number of researchers have established, by the gene-
ralization of empirical data available for some continents,
the morphological diversity of microorganisms about
1000 million years ago [1-8]. This was assumed to have
been related to sexual reproduction in algae at the time.
However, reliable facts regarding sexual reproduction
during the Neoproterozoic (1000 - 542 Ma) have not
been established. That is why the conclusions made by
paleontologists concerning sexual reproduction taking
place during the early stages of life history were regarded
by many biologists as merely speculative [9].
2. The Necessity to Find Evidence f o r S e x u a l
Reproduction
Thin sections of Proterozoic and, particularly, Neopro-
terozoic black cherts and macerated slides of black mud-
stones show that at that time the reproduction of Cyano-
bacteria and algae was asexual and occurred by cell divi-
sion.
However, this is the simplest form of reproduction. It
could not have produced the morphological diversity of
the individuals observed in the Neoproterozoic in some
continents. Therefore, it was necessary to find cogent
evidence for sexual reproduction allowing for a transfer
of genetic information (DNA) between contacting cells,
since it was the transfer that ensured an increase of ge-
netic variability in organisms [9].
With this in mind, the author studied over a thousand
slides (made after the maceration of mudstones by oxi-
dants) and thin sections of black cherts syngenetic with
the host rocks. As a result, evidence for sexual reproduc-
tion in fossil algae was found in sample IV-36 collected
from the Neoproterozoic Kumakhin formation of the La-
khanda group (Figure 1).
3. Geology of the Area, Where Evidence for
Sexual Reproduction Was Found
The geological structure known as the Sette-Daban horst-
anticlinorium is located in northeast Asia, in the junction
zone between the southeastern margin of the Siberian
platform and the Verkhoyansk-Chukotka Mesozoides.
The Meso- and Neoproterozoic (1600 - 545 Ma) sections
of the region are among the most complete in the world,
and have been carefully studied. The territory is referred
to in geological literature as the Yudoma-Maya zone of
the Uchur-Maya region. The Lakhanda and Uya groups
of the region are assigned to the Neoproterozoic (1000 -
545 Ma). The diversified microbiota of the Lakhanda
group has been investigated by many micropaleontolo-
gists (4, 6, 10). It provides an illuminating example of the
morphological diversity of microorganisms existing from
1000 Ma onwards. The Kumakhin formation is the low-
est subdivision of the Lakhanda group. The age of its
basal layers is close to 1000 Ma [11,12].
In Kumakhin times, a warm, shallow-water sea existed
in the Uchur-Maya region, which provided favorable
conditions for the thriving of microorganisms. For this
reason, stromatolites were common there, especially dur-
ing the second part of this time interval [11].

Sexual Reproduction One Billion Years Ago 384
Figure 1. Location and stratigraphy of the Neoproterozoic
Kumakhin formation, northeastern Asia.
The section from where sample IV-36 was collected is
within the Sette-Daban area, in the Aldan river basin
(Figure 1). It includes the Tzipanda (recrystallized and
oncolitic dolomites, 350 m) and Kumakhin (stromatoli-
thic dolomites, mudstones, and siltstones, 190 m) forma-
tions.
Within the same Uchur-Maya region, southeast of the
sampling area (Figure 1), along the Maya river (right
tributary of Aldan), the upper 20 m of the Kumakhin
formation consist of mudstones. The microfossils ex-
tracted from them after maceration include organic wall-
ed coccoid and filamentous microorganisms, as well as
relatively large spheroids (200 - 500 μm) with spines on
the surface (Trachyhistrichosphaera) [5,6]. This spheroid
with spines is an additional evidence for age (about 1000
mln years ago) of the Kumakhin formation, where IV-36
sample was taken.
4. Rock Material and Methods of Its Study
The sample described was taken from a lens of black
chert syngenetic with the enclosing dolomite, 21 km
away from the base of the Kumakhin formation. 15 thin
sections of the sample were prepared and studied using a
NU-2 CARL ZEISS JENA × 1000 microscope. A large
number of silicified spheroidal fossilized microorganisms
have been found, similar to the coccoid cyanobacteria
and algae, i.e. lower organisms without nucleus, des-
cribed earlier from the Neoproterozoic black cherts of
Australia, Canada, China, Russia, and other countries
[1,4,5,10,13,14]. They exhibit the closest resemblance to
Gloeodiniopsis, Myxoccoides, and Glenobothrydion known
from the Neoproterozoic Bitter Springs formation in cen-
tral Australia [13,14]. They occur singly or in colonies.
The spheroids range from 24 to 33 μm in diameter and
have a one- or two-layered membrane 0.4 to 3.6 μm thick
(Figure 2(a)). Reproduction is by binary fission (Figure
2(b)).
5. Material Discussion
The discovered incidence of cell fusion can be easily
explained by recent algae studies [9,15,16]. This type of
fusion differs from both the simple cell dividing process
and from the fusion of two daughter cells after cell divi-
sion, like in some Cyanobacteria (Chroococcus) [15].
The objects shown in Figure 2(b) are hypothetically fos-
silized cells.
They have no flagellum. However, we can see that one
smaller cell (hypothetical male cell) with diameter 19.1
μm has moved to a larger non motile cell (hypothetical
egg cell) with diameter 21.6 μm. The male cell is slightly
pressed into the egg cell (Figure 2(b)).
Their fusion shows that they were in a vegetative state,
and are reminiscent of gametes.
After the fusion of two vegetative cells, the content of
the male cell transfused to the female cell, probably via
conjugation channel. The results of these events are fer-
tilization and further diploid zygote formation inside the
maternal cell.
On Figure 2(b) we can see that the growing zygote
almost reached the cell wall of the maternal cell.
The transfusion of content from one cell to another via
conjugation channel and the internal growth of a zygote
is typical for recent algae [16].
Thus, we have proof of a sexual process.
In Eubacteria, cells do not fuse during their sexual re-
production; in Cyanobacteria [15] a typical sexual re-
production process has not been revealed either. Hence,
the organisms we found were single-celled fossilized
algae, i.e. lower water plants with nucleus. Morphologi-
cally they look like simple unicellular organisms, how-
ever, the revealed sexual process tells us about their ad-
vanced physiology.
This, obviously, allowed them to adapt better to the
often varying conditions of epicontinental basins of the

Sexual Reproduction One Billion Years Ago 385
(a)
(b)
Figure 2. Microfossils from the Kumakhin formation. (a):
Microorganism fertilization by cell dividing into two parts;
(b): Maternal cell fertilization, resulting in diploid zygote
formation. Scale equals 10 mkm.
Neoproterozoic. It results in the morphological diversity
about 1000 million years ago, mentioned in introduction.
6. Conclusions
Whatever we call this type of sexual reproduction, holo-
gamy, conjugation, or anisogamy, this great evolutionary
advance that led to intergenerational change and to the
appearance of organisms with dual heredity, happened no
later than 1000 million years ago.
Now it is not just a supposition as it was before [9],
but an obvious fact.
According to the evolution of modern organic world, it
is well known that genetic information is transferred be-
tween contacting cells during sexual reproduction. DNA
transfer ensures an increase of genetic variability in or-
ganisms. Therefore, organisms become evolutionarily ad-
vanced, their development and acquisition of different
morphologies accelerate.
The increased number of individuals (number of stro-
matolitic layers) and the morphological diversity of algae
in the Tonian (1000 - 850 millions years ago) and the
Cryogenian (850 - 650 millions years ago) were the re-
sult of the sexual reproduction process and genetic re-
combination.
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