Memories of past lives

A Theory Grounded in Molecular Genetics

It is common for lay individuals to encounter, through mass media channels, reports discussing or even demonstrating alleged regressions to past lives or incarnations. Many of these programs depict psychologists performing hypnosis on patients, guiding them to uncover, in their supposed previous existence or “past incarnation,” the origins of their current psychological or physical conditions.

A considerable portion of the population firmly believes in reincarnation, perceiving it as an intangible and unquestionable doctrine. In contrast, a substantial number of individuals—both within the general audience and in broader society—prefer to avoid engaging in such discussions altogether.

Doctrinal Perspectives and a Molecular Genetics Hypothesis
According to leading scholars of Spiritism, when an individual dies, the soul detaches from the physical body and subsequently reincarnates into another body that is being formed at that precise moment through fertilization. Alternatively, it is proposed that the soul may remain in a transitional state—wandering through space or time—until an appropriate physical vessel becomes available.

If this doctrine were to hold true, the phenomenon of regression to past lives would, therefore, rest upon the premise of an immortal soul that migrates from one body to another, perpetuating itself across generations, time, and space.

However, even if the Spiritist theory is not accepted—which is not the focus of this discussion—it remains conceivable that certain recollections or vivid impressions experienced during sleep or under hypnosis could represent memories seemingly derived from other lives, bodies, or temporal contexts. To approach this notion from a scientific standpoint, one may consider the molecular structure of deoxyribonucleic acid (DNA) as elucidated by J. D. Watson and F. H. C. Crick in 1953. Their model proposed that DNA consists of two complementary polynucleotide strands coiled around each other, forming the characteristic double-helix configuration.

Each of these strands is composed of a specific sequence of nucleotides. In turn, each nucleotide consists of a nitrogenous base—either a purine or a pyrimidine—linked to a pentose sugar (deoxyribose) and a phosphate group (PO₄). The nucleotides within each strand are connected through phosphodiester bonds, which link the phosphate group of one nucleotide to the deoxyribose of the adjacent nucleotide.

The two complementary polynucleotide chains are held together by hydrogen bonds formed between the nitrogenous bases of opposing strands.

This structural model led to the conclusion that DNA replication must occur through an apparently simple mechanism. Two major hypotheses were subsequently formulated to explain this process:

• Conservative replication hypothesis: This model proposed that the original DNA double helix served as a template guiding the formation of an entirely new molecule while remaining structurally intact itself. Consequently, after replication, one would obtain a completely new DNA molecule and one original (parental) molecule that remained unaltered.

• Semiconservative replication hypothesis: According to this model, if DNA consists of two complementary strands, each strand could serve as a template for the synthesis of a new complementary strand once the hydrogen bonds between the paired nucleotides were disrupted. The result of this process would be two DNA molecules, each composed of one parental and one newly synthesized strand.

The second hypothesis prevailed when, in 1958, Matthew Meselson and Franklin Stahl published the results of an experiment designed to determine which model best explained the mechanism of DNA replication.

Strains of Escherichia coli were cultivated for several generations in a medium containing the heavier isotope of nitrogen, N¹⁵, instead of the naturally abundant N¹⁴. Since nitrogenous bases incorporate nitrogen from their growth medium into their molecular structure, the DNA of cells grown in the N¹⁵ medium exhibited a greater density than that of cells cultivated in a normal N¹⁴ environment.

Subsequently, the N¹⁵-labeled bacteria were transferred to a medium containing only N¹⁴. When samples were analyzed by equilibrium density-gradient centrifugation, the conservative model predicted the formation of two distinct bands: a heavy (N¹⁵/N¹⁵) and a light (N¹⁴/N¹⁴) DNA fraction. In contrast, the semiconservative model predicted the presence of a single intermediate-density band (N¹⁵/N¹⁴), representing hybrid molecules.

The results obtained by Meselson and Stahl were fully consistent with the semiconservative replication model. After a defined period of cell division, only hybrid DNA molecules (N¹⁵/N¹⁴) were observed, with no evidence of distinct heavy or light bands.

In simplified terms, this means that the two strands of the original DNA molecule separate, and each serves as a template for the synthesis of a new complementary strand. The two resulting DNA molecules thus consist of one parental (old) and one newly synthesized (new) strand. Within these parental strands are preserved all the informational determinants inherited from the original cell.

The central question, therefore, is as follows: if DNA replicates in a semiconservative manner—producing a new molecule composed of one parental and one newly synthesized strand—it is conceivable that the parental strand may retain informational patterns beyond those merely associated with genetic coding. One could hypothesize that such an ancestral strand might contain molecular configurations potentially related to the development of neural nuclei and, hypothetically, to the encoding of sensory or cognitive information, such as visual or auditory memory traces, or even experiences once lived by other individuals who carried the same molecular lineage through previous fertilizations.

Possible Sites of Molecular Implantation
A fundamental question arises: where could such ancestral DNA strands theoretically be integrated or expressed?

From an evolutionary standpoint, the nervous system in animals originates with the Porifera (marine sponges), organisms that already exhibit a primitive “neural system” composed of sensory nodes dispersed throughout the body and interconnected by nerve-like fiber bundles reminiscent of the nervous tracts observed in more evolved species.

The first organisms to develop a true central nervous system were the fishes, belonging to the phylum Chordata—animals characterized by the presence of a notochord, at least during their embryonic stage, as occurs in humans.

In fish, only the archicortex is present, functioning as the principal neural substrate responsible for regulating instinctive and vital organic functions. These patterns of neural organization and instinctual behavior are transmitted genetically from the parents to their offspring through the inherited genotype. This observation, in fact, refines the popular saying “like father, like son,” suggesting that, more precisely, “the offspring of a fish is a fry”—a direct genetic and neurobiological continuity rather than mere resemblance.

In amphibians, the paleocortex emerges for the first time, while in reptiles, rudimentary traces of a neocortex can already be identified. Among birds, the neocortex becomes slightly more developed, and in mammals it expands considerably, occupying most of the cerebral hemispheres.

In humans, the archicortex is located primarily within the hippocampal formation; the paleocortex corresponds largely to the parahippocampal gyrus; and the neocortex encompasses the remaining cortical regions, extending from the cingulate gyrus—the center of emotional and cognitive integration—to the outer cortical zones responsible for sensory and motor control. Within these regions, distinct gyri are associated with specific sensory modalities: the precentral gyrus mediates tactile and motor responses, the postcentral gyrus processes sensations such as pain, temperature, and pressure, the temporal gyrus is responsible for auditory perception, the frontal gyrus for speech production, and the occipital gyrus for visual processing.

It is well established that the archicortex governs instinctive behaviors, which are genetically transmitted and species-specific—in the human case, these correspond to innate survival and reproductive patterns. The paleocortex integrates mixed information, encompassing both learned and genetically encoded behaviors, whereas the neocortex is primarily responsible for the acquisition, storage, and processing of learned information. Within this region, electrical and synaptic activity underlies voluntary and cognitively mediated movements (such as grasping, releasing, running, striking, writing, thinking, and reasoning), as well as the perception of sensory inputs including pain, temperature, and touch.

Based on these functional distinctions, the human brain may be conceptually divided, drawing upon frameworks from psychoanalysis, behaviorism, bioenergetics, and related branches of psychology, as follows:

The archicortex may be functionally correlated with the unconscious mind, the paleocortex with the preconscious, and the neocortex with the conscious level of mental activity. This correspondence provides an interesting neurobiological framework for classical psychoanalytic theory, suggesting a hierarchical integration of instinctive, emotional, and rational processes within the brain’s evolutionary architecture.

From a neuroanatomical perspective, examination of standard neuroanatomy texts reveals that the hippocampus communicates with the parahippocampal gyrus through the fimbria of the hippocampus, while the parahippocampal gyrus connects to the cingulate gyrus via the isthmus of the cingulate gyrus. These pathways form part of a complex limbic circuitry involved in emotional regulation, memory consolidation, and the modulation of conscious and unconscious cognitive states.

The deepest forms of memory—those that profoundly shape an individual’s life experience, as well as those sometimes described as recollections from “previous incarnations”—are presumably stored within the unconscious mind, and thus within the archicortex. From an evolutionary perspective, the human brain, like that of other animals, developed outward from the archicortex toward the neocortex. This progressive cortical expansion represents the principal neurobiological distinction between Homo sapiens sapiens and other animal species.

Since the archicortex governs instinctive and innate survival behaviors and is itself primarily regulated by genetic programming, it can be theoretically proposed that this region may also retain chromosomal sequences containing molecular codes related to ancestral memory patterns—that is, traces of experiences lived by predecessors in prior biological existences. This interpretation, however, should not be confused with the spiritual notion of “reincarnation,” but rather understood as a biogenetic continuity of informational substrates.

An additional point supporting this hypothesis is the observation that human infants are born with innate and instinctive behaviors, such as sucking and crying. These were first described by August Weismann (1883), who formulated the Theory of the Continuity of the Germ Plasm, proposing that parents transmit their “germ plasm—the immortal component of living beings”—to their offspring via the sexual gametes. It is now known that Weismann’s “germ plasm” corresponds to what we recognize today as the chromosomal material contained within human reproductive cells.

The concepts presented herein constitute a theoretical proposition, open to discussion and critical evaluation by all interested scholars. The intention of this work is not to establish definitive conclusions, but rather to encourage reflection and interdisciplinary dialogue at the interface of molecular genetics, neurobiology, psychology, and the study of memory phenomena.

References

1. Gardner E, Snustad DP. Genetics. 7th ed. Rio de Janeiro: Guanabara Press; 1986.
2. Lessnau R. Structure of DNA. In: Nature and Function of Genetic Material [software]. Curitiba: Federal University of Paraná Press (UFPR); 1996.
3. Lessnau R. DNA Replication. In: Nature and Function of Genetic Material [software]. Curitiba: Federal University of Paraná Press (UFPR); 1996.