Evolutionary Significance of Altered States of Consciousness

On the Necessity of Nervous System Flexibility and Related Questions

26/07/2026 · 19 min read

Introduction

The hu­man brain’s abil­i­ty to en­ter al­tered states of con­scious­ness is one of the most strik­ing man­i­fes­ta­tions of the ner­vous sys­tem’s flex­i­bil­i­ty. Through­out hu­man his­to­ry, these states have ap­peared in many dif­fer­ent forms and cul­tur­al con­texts—dur­ing re­li­gious rit­u­als, med­i­ta­tion, dance, singing, child­birth, in­tense phys­i­cal ex­er­tion, deep in­ter­per­son­al close­ness, in cri­sis sit­u­a­tions, or dur­ing spe­cif­ic forms of phys­i­cal ex­pe­ri­ence. Al­though these states can be sub­jec­tive­ly very dif­fer­ent, their com­mon fea­ture is a tem­po­rary change in the way the ner­vous sys­tem or­ga­nizes per­cep­tion, at­ten­tion, emo­tions, bod­i­ly sig­nals, and a per­son’s re­la­tion­ship to their own self.

From the per­spec­tive of a com­mon, in­tu­itive un­der­stand­ing of con­scious­ness, al­tered states may seem ex­tra­or­di­nary or un­usu­al. How­ev­er, con­tem­po­rary neu­ro­bi­ol­o­gy of­fers a dif­fer­ent view. The hu­man brain is not a hard-wired sys­tem with a sin­gle op­ti­mal mode of func­tion­ing. On the con­trary, one of its most sig­nif­i­cant char­ac­ter­is­tics is the abil­i­ty to change its func­tion­al or­ga­ni­za­tion ac­cord­ing to cur­rent bi­o­log­i­cal, en­vi­ron­men­tal, and so­cial con­di­tions.

From this per­spec­tive, the main ques­tion is not why the hu­man brain some­times cre­ates al­tered states of con­scious­ness, but why evo­lu­tion­ary process­es led to the emer­gence of a ner­vous sys­tem that al­lows such ex­ten­sive changes in the first place. Why does the or­gan­ism have mech­a­nisms ca­pa­ble of al­ter­ing the per­cep­tion of time, space, pain, bod­i­ly sen­sa­tions, emo­tions, or the sub­jec­tive sense of iden­ti­ty?

The an­swer is tied to the very na­ture of bi­o­log­i­cal adap­ta­tion. Evo­lu­tion does not cre­ate or­gan­isms as sta­t­ic ma­chines op­ti­mized for only one spe­cif­ic sit­u­a­tion. Liv­ing sys­tems must func­tion in en­vi­ron­ments that are con­stant­ly chang­ing, con­tain un­cer­tain­ty, and of­ten re­quire dif­fer­ent sur­vival strate­gies. There­fore, an or­gan­ism doesn’t just need the abil­i­ty to re­act ef­fec­tive­ly. It also needs the abil­i­ty to change how it re­acts.

Evo­lu­tion­ary Premise: This flex­i­bil­i­ty does not mean that every spe­cif­ic al­tered state of con­scious­ness rep­re­sents a dis­tinct, pur­pose­ful­ly evolved adap­ta­tion. While we do not know with cer­tain­ty the ex­act evo­lu­tion­ary pur­pose of many of these states, we es­ti­mate that many bi­o­log­i­cal abil­i­ties arise rather as part of broad­er sys­temic prop­er­ties and are sub­se­quent­ly uti­lized in var­i­ous sit­u­a­tions. The abil­i­ty to en­ter al­tered states of con­scious­ness did not nec­es­sar­i­ly evolve so that the or­gan­ism could achieve spe­cif­ic types of ex­pe­ri­ences, but like­ly be­cause the ner­vous sys­tem gained an ex­tra­or­di­nary abil­i­ty to re­or­ga­nize it­self based on what ap­pears most ap­pro­pri­ate in a giv­en mo­ment.

The Evolution of the Nervous System as the Evolution of Flexibility

The brain is among the most en­er­gy-de­mand­ing or­gans in the hu­man body. Even though it rep­re­sents only a rel­a­tive­ly small por­tion of body weight, it con­sumes a sig­nif­i­cant amount of meta­bol­ic re­sources. From an evo­lu­tion­ary per­spec­tive, it is there­fore un­like­ly that the ex­ten­sive reg­u­la­to­ry mech­a­nisms of the ner­vous sys­tem would per­sist with­out pro­found sig­nif­i­cance for the or­gan­ism’s func­tion­ing. Cur­rent find­ings sug­gest that the brain’s abil­i­ty to adapt its own func­tion­al state is not mere­ly a ran­dom byprod­uct of neu­ronal ac­tiv­i­ty. It like­ly re­flects a fun­da­men­tal prop­er­ty of the ner­vous sys­tem that en­ables the adap­tive reg­u­la­tion of be­hav­ior and phys­i­o­log­i­cal process­es. It is as­sumed to stem from the core op­er­at­ing prin­ci­ple of the ner­vous sys­tem—the need to con­tin­u­ous­ly ad­just be­hav­ior, at­ten­tion, emo­tions, and bod­i­ly reg­u­la­tion to cur­rent con­di­tions.

This prin­ci­ple is fun­da­men­tal­ly dif­fer­ent from the idea of the brain as a de­vice whose sole task is to ac­cu­rate­ly and pas­sive­ly record the sur­round­ing re­al­i­ty. Con­tem­po­rary neu­ro­sci­en­tif­ic mod­els view the brain as an ac­tive reg­u­la­to­ry sys­tem that con­stant­ly eval­u­ates the state of the or­gan­ism, the en­vi­ron­ment, and so­cial sit­u­a­tions. Bi­o­log­i­cal­ly, it is not op­ti­mal to ex­ist per­pet­u­al­ly in the same set­ting, be­cause every sit­u­a­tion re­quires a dif­fer­ent way of pro­cess­ing in­for­ma­tion. An or­gan­ism fac­ing an im­me­di­ate threat needs quick ori­en­ta­tion, high sen­si­tiv­i­ty to dan­ger, and the ca­pac­i­ty for in­stant phys­i­cal re­ac­tion. Con­verse­ly, an or­gan­ism in a safe en­vi­ron­ment can al­lo­cate its re­sources en­tire­ly dif­fer­ent­ly—for learn­ing, so­cial con­nec­tion, re­gen­er­a­tion, cre­ativ­i­ty, or long-term plan­ning.

In this eval­u­a­tion process, the brain doesn’t just work with the ques­tion “What is hap­pen­ing right now?” but si­mul­ta­ne­ous­ly ad­dress­es:

• “What is like­ly to hap­pen next?”
• “How sig­nif­i­cant is this in­for­ma­tion?”
• “What mode of re­sponse will be most ap­pro­pri­ate in this sit­u­a­tion?”

This prin­ci­ple is the foun­da­tion of the pre­dic­tive cod­ing the­o­ry of the ner­vous sys­tem. Ac­cord­ing to this mod­el, the brain con­stant­ly gen­er­ates mod­els of fu­ture events and com­pares them with new­ly in­com­ing in­for­ma­tion. If the ex­pec­ta­tions and re­al­i­ty match, the or­gan­ism can func­tion ef­fi­cient­ly and with low­er en­er­gy de­mands. How­ev­er, if a dis­crep­an­cy aris­es, a so-called pre­dic­tion er­ror oc­curs.

A pre­dic­tion er­ror is not a sign that the brain sim­ply made a mis­take. It is con­sid­ered one of the most cru­cial mech­a­nisms for learn­ing and adap­ta­tion. It in­forms the ner­vous sys­tem that its cur­rent mod­el of the sit­u­a­tion is not ac­cu­rate enough and needs to be ad­just­ed. An or­gan­ism ca­pa­ble of us­ing pre­dic­tion er­rors to up­date its in­ter­nal mod­els gains the abil­i­ty to re­act more quick­ly to new con­di­tions. It is pre­cise­ly this con­stant up­dat­ing that is the prob­a­ble rea­son why the hu­man brain is not rigid­ly con­fined to a sin­gle mode of func­tion­ing.

The ner­vous sys­tem like­ly op­er­ates as a dy­nam­ic net­work of var­i­ous reg­u­la­to­ry modes. These modes are not hi­er­ar­chi­cal­ly or­ga­nized such that one is “cor­rect” and the oth­ers are in­fe­ri­or. Each rep­re­sents an adap­tive con­fig­u­ra­tion suit­ed for spe­cif­ic con­di­tions.

From this view­point, al­tered states of con­scious­ness can be un­der­stood as sit­u­a­tions where there is a tem­po­rary shift in the pri­or­i­ties of in­di­vid­ual sys­tems. Cer­tain forms of in­for­ma­tion pro­cess­ing are am­pli­fied, while oth­ers lose promi­nence. At­ten­tion may shift from the ex­ter­nal en­vi­ron­ment to in­ter­nal bod­i­ly process­es, an­a­lyt­i­cal con­trol may give way to di­rect ex­pe­ri­ence, and so­cial or emo­tion­al in­for­ma­tion may gain more weight than stan­dard cog­ni­tive eval­u­a­tion.

There­fore, this process is not re­lat­ed to a fail­ure of reg­u­la­tion but rep­re­sents the very man­i­fes­ta­tion of its ca­pa­bil­i­ty and flex­i­bil­i­ty.

Altered States of Consciousness as an Adaptive Mechanism

If we ac­cept the premise that the fun­da­men­tal evo­lu­tion­ary ad­van­tage of the hu­man brain is the ca­pac­i­ty for adap­tive change, then al­tered states of con­scious­ness no longer ap­pear as ex­cep­tions. Sub­jec­tive ex­pe­ri­ence aris­es from the in­te­gra­tion of many par­al­lel process­es, in­clud­ing sen­so­ry per­cep­tion, bod­i­ly reg­u­la­tion, emo­tion­al ap­praisal, mem­o­ry, at­ten­tion, mo­ti­va­tion, and the abil­i­ty to con­struct a self-mod­el. The or­di­nary state of con­scious­ness rep­re­sents just one spe­cif­ic con­fig­u­ra­tion of these sys­tems.

Con­tem­po­rary neu­ro­science is there­fore in­creas­ing­ly aban­don­ing the idea of con­scious­ness as a sta­t­ic state, lean­ing to­wards the hy­poth­e­sis that it is a dy­nam­ic process emerg­ing from the co­or­di­nat­ed ac­tiv­i­ty of wide­spread neur­al net­works. Thus, a change in con­scious­ness does not nec­es­sar­i­ly mean a dis­rup­tion of brain func­tion, but rather a shift in how these in­di­vid­ual sys­tems col­lab­o­rate.

One of the key prin­ci­ples of this re­or­ga­ni­za­tion is the re­al­lo­ca­tion of at­ten­tion. At­ten­tion is a lim­it­ed bi­o­log­i­cal re­source. At­ten­tion­al se­lec­tiv­i­ty is cru­cial for sur­vival: in an en­vi­ron­ment full of in­for­ma­tion, the or­gan­ism must con­stant­ly de­cide which stim­uli to de­vote en­er­gy to and which to ig­nore. A hunter track­ing an an­i­mal, a par­ent re­spond­ing to a child’s sig­nals, an ath­lete dur­ing per­for­mance, or a per­son in a cri­sis sit­u­a­tion all uti­lize a sim­i­lar prin­ci­ple: the ner­vous sys­tem tem­porar­i­ly high­lights a spe­cif­ic part of re­al­i­ty and sup­press­es in­for­ma­tion that is not a pri­or­i­ty at that giv­en mo­ment.

Al­tered states of con­scious­ness of­ten in­volve pre­cise­ly this kind of dra­mat­ic shift in the dis­tri­b­u­tion of at­ten­tion. Broad en­vi­ron­men­tal mon­i­tor­ing can be re­placed by an in­tense fo­cus on in­ter­nal bod­i­ly sen­sa­tions, emo­tion­al states, or the ac­tiv­i­ty process it­self.

Note: The fol­low­ing overview should be read as a set of the­o­ret­i­cal hy­pothe­ses de­rived pri­mar­i­ly from re­search on oth­er well-doc­u­ment­ed states (med­i­ta­tion, pain, so­cial bond­ing, sleep) and ap­plied to a broad­er spec­trum of phe­nom­e­na—for many of these (es­pe­cial­ly sub­space, hyp­not­ic trance, or crowd trance), di­rect neu­roimag­ing data is prac­ti­cal­ly nonex­is­tent:

From an evo­lu­tion­ary per­spec­tive, it is pre­cise­ly this abil­i­ty to shift the bal­ance be­tween cog­ni­tive con­trol and open­ness to ex­pe­ri­ence that is sig­nif­i­cant. In an en­vi­ron­ment where it is nec­es­sary to quick­ly an­a­lyze risks and plan for the fu­ture, a high de­gree of con­trol is ad­van­ta­geous. How­ev­er, in an en­vi­ron­ment of safe­ty, we es­ti­mate it may be more adap­tive to al­low for greater sen­si­tiv­i­ty to bod­i­ly sig­nals, emo­tions, and so­cial in­for­ma­tion.

Social Regulation, Safety, and the Importance of Relational States

The hu­man brain ex­hibits pro­found­ly re­la­tion­al char­ac­ter­is­tics. A sig­nif­i­cant part of its de­vel­op­ment oc­curred with­in so­cial groups, where an in­di­vid­ual’s sur­vival de­pend­ed not mere­ly on re­act­ing in­de­pen­dent­ly to phys­i­cal stim­uli, but pri­mar­i­ly on the abil­i­ty to form sta­ble bonds, co­op­er­ate, and mu­tu­al­ly reg­u­late in­ter­nal states.

Hu­mans have de­vel­oped an ex­cep­tion­al­ly strong abil­i­ty to use the pres­ence of an­oth­er in­di­vid­ual as a source of bi­o­log­i­cal reg­u­la­tion. This mech­a­nism is cru­cial from birth. An in­fant’s ner­vous sys­tem can­not in­de­pen­dent­ly sta­bi­lize its process­es (tem­per­a­ture, stress re­spons­es, emo­tion­al ten­sion); it is soothed by re­spond­ing to a care­giv­er’s so­cial sig­nals—tone of voice, touch, fa­cial ex­pres­sions, and body heat. These pieces of in­for­ma­tion seem­ing­ly rep­re­sent di­rect bi­o­log­i­cal sig­nals of en­vi­ron­men­tal safe­ty for the de­vel­op­ing brain.

In adult­hood, this mech­a­nism does not dis­ap­pear; it mere­ly be­comes more com­plex. We re­fer to this process as so­cial or re­la­tion­al co-reg­u­la­tion. It is not that one per­son di­rect­ly con­trols an­oth­er’s ner­vous sys­tem; it is more ac­cu­rate to es­ti­mate that it is a con­tin­u­ous ex­change of bi­o­log­i­cal in­for­ma­tion, where one per­son’s ner­vous sys­tem pro­vides sig­nals to the oth­er, by which they can ad­just their own state. For a species whose sur­vival re­lies on co­op­er­a­tion, the abil­i­ty to quick­ly build trust and re­duce ten­sion with­in a group is a mas­sive evo­lu­tion­ary ad­van­tage.

Here lies the fun­da­men­tal dif­fer­ence be­tween the in­ten­si­ty of a phys­i­cal ex­pe­ri­ence and its bi­o­log­i­cal in­ter­pre­ta­tion. The ner­vous sys­tem doesn’t mere­ly re­act to the me­chan­i­cal force of a stim­u­lus, but con­stant­ly eval­u­ates its mean­ing in a broad­er con­text. This prin­ci­ple is clear­ly ev­i­dent in the ex­am­ple of pain:

The brain doesn’t just ask: “How strong is this sig­nal from the re­cep­tors?” It si­mul­ta­ne­ous­ly asks: “What does this sig­nal mean in this con­text, and how should I re­act to it?”

The ner­vous sys­tem con­structs the com­plex ex­pe­ri­ence of pain through a com­bi­na­tion of sen­so­ry in­for­ma­tion, ex­pec­ta­tions, emo­tion­al state, and cur­rent con­text. This is why an ath­lete fin­ish­ing a gru­el­ing per­for­mance, a moth­er dur­ing child­birth, or a per­son un­der­go­ing a con­scious­ly cho­sen in­ten­sive process per­ceives bod­i­ly sig­nals com­plete­ly dif­fer­ent­ly than some­one ex­pe­ri­enc­ing a sud­den, un­ex­pect­ed in­jury.

Thanks to this in­ter­pre­tive abil­i­ty, a per­son can un­der­go de­mand­ing phys­i­cal ex­pe­ri­ences with­out every strong sig­nal au­to­mat­i­cal­ly trig­ger­ing a de­fen­sive, stress re­sponse. If the or­gan­ism eval­u­ates the en­vi­ron­ment and re­la­tion­ship as safe, it can re­lease re­sources that it would oth­er­wise ded­i­cate to de­fense and con­trol. Bod­i­ly sig­nals can be in­te­grat­ed with­out be­ing ap­praised as a threat, which, ac­cord­ing to our cur­rent es­ti­mates, opens the door for the emer­gence of pro­found al­tered states of con­scious­ness.

Partner Intimacy as a Natural Context for Altered States

Part­ner in­ti­ma­cy rep­re­sents one of the most promi­nent con­texts in which the mech­a­nisms of so­cial reg­u­la­tion, bod­i­ly ex­pe­ri­ence, and the al­tered set­tings of the ner­vous sys­tem in­ter­twine. In a safe re­la­tion­al en­vi­ron­ment, a nat­ur­al shift in pri­or­i­ties oc­curs: at­ten­tion moves away from mon­i­tor­ing ex­ter­nal risks to­ward a more in­tense per­cep­tion of the body, emo­tions, and non­ver­bal com­mu­ni­ca­tion.

While we in­tel­lec­tu­al­ly un­der­stand that a high lev­el of cog­ni­tive con­trol is es­sen­tial in every­day func­tion­ing (it al­lows us to plan, make de­ci­sions, and pro­tect our bound­aries), in a safe in­ti­mate con­text, it ap­pears adap­tive to tem­porar­i­ly low­er this con­trol. This state can­not be un­der­stood as pas­siv­i­ty or a loss of au­ton­o­my; con­verse­ly, we as­sume it re­quires high­ly pre­cise, un­con­scious reg­u­la­tion. The ner­vous sys­tem must con­stant­ly ver­i­fy whether the part­ner re­mains trust­wor­thy, whether bound­aries are re­spect­ed, and whether the en­vi­ron­ment is safe. Open­ness to in­tense ex­pe­ri­ence is like­ly un­der­pinned to a large ex­tent by this on­go­ing eval­u­a­tion of safe­ty.

From a neu­ro­bi­o­log­i­cal stand­point, in­ti­ma­cy con­nects sev­er­al evo­lu­tion­ar­i­ly old­er sys­tems: so­cial bond­ing, the re­ward sys­tem, stress reg­u­la­tion, and learn­ing. In­tense ex­pe­ri­ences in this con­text gain tremen­dous sig­nif­i­cance be­cause they in­te­grate mul­ti­ple lay­ers of pro­cess­ing si­mul­ta­ne­ous­ly—bod­i­ly, emo­tion­al, so­cial, and cog­ni­tive.

We can only sur­mise and es­ti­mate ex­act­ly how the ner­vous sys­tem stores these ex­pe­ri­ences, but cur­rent the­o­ry sug­gests it uses them to up­date its mod­els of the world. If a per­son re­peat­ed­ly ex­pe­ri­ences that open­ness, vul­ner­a­bil­i­ty, or in­tense phys­i­cal sen­sa­tions can safe­ly un­fold in a re­spect­ful en­vi­ron­ment, in­ter­nal pre­dic­tive mod­els are grad­u­al­ly up­dat­ed. There are also like­ly changes in synap­tic plas­tic­i­ty that can man­i­fest as a long-term shift in how sim­i­lar sit­u­a­tions are processed. The or­gan­ism doesn’t just learn through ra­tio­nal think­ing, but through the lived ex­pe­ri­ence of the whole body.

Altered States of Consciousness, Neuroplasticity, and Learning

From a sur­vival per­spec­tive, an or­gan­ism would de­rive no ben­e­fit from mere­ly feel­ing ex­pe­ri­ences in­tense­ly if it couldn’t change its fu­ture be­hav­ior based on them. There­fore, a sig­nif­i­cant prop­er­ty of the ner­vous sys­tem is neu­ro­plas­tic­i­ty—the brain’s abil­i­ty to change its own struc­ture and func­tion­al or­ga­ni­za­tion based on ex­pe­ri­ence.

How­ev­er, the brain does not learn from all sit­u­a­tions equal­ly. If it per­ma­nent­ly stored every or­di­nary stim­u­lus, it would be over­whelmed. A more evo­lu­tion­ar­i­ly ad­van­ta­geous strat­e­gy is se­lec­tive learn­ing. Sit­u­a­tions as­so­ci­at­ed with a high de­gree of mean­ing, in­ten­si­ty, or sur­prise trig­ger mech­a­nisms that like­ly in­crease the prob­a­bil­i­ty of their long-term stor­age in the neur­al net­work.

Here again, pre­dic­tive pro­cess­ing and pre­dic­tion er­ror come into play. If we ex­pe­ri­ence a sit­u­a­tion that fun­da­men­tal­ly dis­rupts our pri­or ex­pec­ta­tions, a sig­nif­i­cant pre­dic­tion er­ror oc­curs. We as­sume the ner­vous sys­tem flags it as po­ten­tial­ly im­por­tant and grants it in­creased plas­tic­i­ty to ad­just in­ter­nal mod­els of re­al­i­ty for the fu­ture.

Cru­cial­ly, con­text is key again—not in the sense that an or­gan­ism in dan­ger doesn’t learn, but in terms of the type of learn­ing the giv­en con­text pro­motes:

• In­tense Ex­pe­ri­ence + Feel­ing of Threat/Be­tray­al: Learn­ing oc­curs here too, of­ten very quick­ly and ef­fec­tive­ly. How­ev­er, the re­sult tends to be the re­in­force­ment and gen­er­al­iza­tion of de­fen­sive strate­gies—in­creased hy­per­vig­i­lance, rigid­i­ty, gen­er­al­iza­tion of fear to sim­i­lar sit­u­a­tions—rather than greater re­sponse flex­i­bil­i­ty. With re­peat­ed or un­man­age­able threats, this pat­tern can con­tribute to the de­vel­op­ment of trau­mat­ic re­spons­es.
• In­tense Ex­pe­ri­ence + Con­text of Safe­ty/Trust/Man­age­abil­i­ty: This cre­ates con­di­tions more suit­ed for adap­tive learn­ing, in­te­gra­tion of ex­pe­ri­ence, and ex­pan­sion of the or­gan­ism’s re­sponse reper­toire.

For ex­am­ple, if a per­son has long ex­pect­ed that vul­ner­a­bil­i­ty or loss of con­trol au­to­mat­i­cal­ly means dan­ger, and in a new con­text re­peat­ed­ly ex­pe­ri­ences that deep sur­ren­der and in­tense bod­i­ly sen­sa­tions oc­cur safe­ly and pre­dictably, this ex­pec­ta­tion can grad­u­al­ly change. This is not a sim­ple “over­writ­ing” or eras­ing of the old pre­dic­tion—the orig­i­nal learned re­sponse may con­tin­ue to ex­ist along­side the new­ly form­ing ex­pec­ta­tion. Which one man­i­fests in a giv­en sit­u­a­tion de­pends on con­text, stress lev­els, and oth­er cir­cum­stances. It is there­fore more ac­cu­rate to speak of the emer­gence of a new, com­pet­ing ex­pec­ta­tion or a re­duc­tion in the prob­a­bil­i­ty of the old re­sponse, rather than its com­plete over­writ­ing.

Al­tered states of con­scious­ness are cir­cum­stances where these process­es can be ac­ti­vat­ed par­tic­u­lar­ly strong­ly. Due to al­tered at­ten­tion and high emo­tion­al rel­e­vance, the brain process­es in­for­ma­tion with ex­tra­or­di­nary sen­si­tiv­i­ty, which can—un­der fa­vor­able con­di­tions—en­able a pro­found re­or­ga­ni­za­tion of the or­gan­ism’s in­ter­nal mod­els.