The environment. Creature genotype. The creatures

Transcription

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XY+Z[P\]Y_^`[Pab\dce9f g=hi^`cibijabkpclh3mcn\d^dajopmajclijibcjeqcjr Y+\`atsvu wvxy4e;cjz{y_^` ~} c Y+^dat 3cls~c^ e9f g=hqƒ [ \d Y_^`ab I ;c p chi^d\`cjwh3ajˆ c\]sraj^`ypaj\`ce;cls qypajhi^`sorš c\`cls Iuq q\` ;ceqcœs qy+abhi^`sorš c\`cls +upžpžp r Y+\`abs Ax3\`YPh3mc c^dabîabc\œ qity_^r^]y+ 3e9 _ V Y_^` q abhqƒ [p ;h3ajî 3Y+\`abs]uq ƒ \ g=hi^`c\`h3y_^`aj[ h3y+i9g=h3sr^daj^d ;^dc[+ƒ z$ ;ij^dab cleqaty; prvš [PibcLwh;abˆPcl\`sda ^]Y+ab\dcXL} c[ h3y+\]e#eqcœvajh3ma Iž+ 3Ÿ XY $} cƒ ch3sdc cle;c x3\`yph3mc PcŒY+hq R ibyp 3eqc c 3eqabh eqclˆ ajh3mä ƒ \ #ª«l _ ; + ± ² ³µ µq ` µp > ]³= ]¹_º>³ O³ º= > ]³=³»½¼ ³= ¾J³=µq ]À]² º>² ÁŒ¹ ÂÁ+¾ `à ² ÂL» µ à ] ]¹_º> ¾ÅÄW²Æº>± ² ¹ÈÇ3²ÆÉt ]Ê~ >ÁlµpË Ì+²Æ =º>Í lãaäá >Ãj¾QÄW²Æº>±Î¼ ² Á» ² ¹ ³=µI²Æ > ¾Ï lðœ `¹+º>³]ÑÓÒ ¹Ôº>±I² ³ÂÁ+¾ `à ËL² ¹I¾ ² Ì+² ¾ Í Ã ³$ > Q¾ ² ³» º= >² ¼ Í º> ¾ ÂÁŒ¹Iг=µq `À]² ]³v³= ]µi Ŗ º> ]¾#¼_Õ JÖl¼ = >² d >Ö Â ]ÀR±» ¹I² ³= µ > ]ÌØ `¹+º>² ¹ ÐLº>±I O > ]µ >Á+¾PÍIÀ`º>² Ál¹Ù¼q dº Ä ` ]¹#² ¹I¾ ² Ì+² ¾ Í Ã ³ ÁɾP²ÆÚ; ` > ]¹_º~³=µq `À]² ]³]ÑÛ ¹# ¹ à ÕP³=² ³vÁÉ ³=µq ]À`² `³O¾PÕP¹ ² À]³ ² ¹ > `Ãj º>² ÁŒ¹º>ÁÙ³ º= > ]³=³² ³LµP > ]³= ]¹_º> ¾3Ñ{ÜA ]³=Í Ã º>³³=±IÁ Ä ¾ ² ÌØ ` >³=²Æº Õ ÂJ ² ¹+º> `¹ l¹ À] l¹ ¾J O > làdº>² ÌŒ ~À µ là`² º Õ ¾ ÍP >² ¹ ÐVÀd >² ³=² ³ ³=²Æº>Í» º>² Ál¹I³ ÉÝ ÌØÁ >² ¹ ÐLº>±I v ` ` >ÐŒ ]¹ À] váé¹i `Ä)³=µq ]À]² ]³]Ñ Þ M 8 1;ßOF EV2 8q: ßAM à ˆPcl\^d ;c iby s>^aeqcœmy eqclsl sdcˆ c\]y+i;sr^d 3eqabclsW[+ƒY+\d^dajopmatY+i3clm[IsRáqsR ^dcl sl 3Y؈PcâZpclchD ; ;Z3ijatsR 3cleQajh^d 3c o3citeå[pƒvn \R^`a omaty+iwxajƒ cp ã ái 3abmlY+ibijá AsR pm] &YQsRáqsR^dc0abh3mij 3e;cls YÅ [P 3 ;iby+^dab[ph&[+ƒvz3aj[p abh3sr 3aj\`cleäY+ ;^d[ph3[p [P 3s YPkPchI^]s åo ;abm] Ôm[P pc^dc^`[èsr ;\`ˆ ajˆ c abhy sdab ;ity_^`cle clhiˆ ab\d[ h; chi^l æ YPm] #Y+k chi^ ats~eqcls`m\`ajzcle# 3s> abh;kçyçk ch;[p^>ái câåo ;abm] è YPs`sR[qmatY_^`cle{^d[Ysd pcœmaty_^`aj[ h clm] ; Y+h3absd 9 ;\d[_ˆ ateqclsy+hcˆ [Pib q^dab[ph3yp\dáç ;\`[qmcls`sv pcl\d aj^r^dabh;kç^d 3c c cl\dk ch3mc [Pƒ~ [P\`c YPe;YP q^dcœeypkpchi^]slajh^d ;c clh Îab\`[Ph; chi^œ n [ h;kj^` ;c qxajƒ cl V\d[ #ats Y Îab\d^d 3YPipcŒm[ sdáqs>^`cém[ h3sratsr^dabh;k [+ƒm\`cly+^d ;\`cls clˆp[ ijˆ abh;kabhêydˆ aj\d^d py+ieq\`[p ä[+ƒlåvy_^dcl\l à h3c [+ƒ ^` ;c [ Zqë>clm^dabˆPcŒsats^`[Ù ;\`[_ˆ abeqc Y [ e;ciƒ [P\Ls>^` 3eqá ajh3k#^d 3c m[ ;ijc qa ^>áè[pƒlsd clmabcls e;áihpy+ abmls abh&^` ;cƒ \]Y+ cå~[p\`ìî[+ƒly ity+\`kpc\ ;\`[+ë>cœm ^Y e;eq\`cls`srabh;kù^d ;cdírclˆp[ ij q^`aj[ hå[pƒ m[ â 3ijc aj^>áqî abhçˆ_yp\dab[p 3svmibY sdsdcls~[+ƒ eqá h3ypâatmypisráqsr^dcl sï cl 3eqabh Ÿl P ð ñ nhù[ \dabkpabh3ypiqƒ cly+^d ;\`c [PƒèXajƒ cl V\d[ #\dclijabclsaajha ^]sa [qeqcliyph3e abâ 3ijclâclhI^`Y_^`aj[ hè[+ƒo^` ;csd clmabclsâm[ h3mcl q^l Åg=hÈ [ sr^ ;\`cˆ aj [P psyp\r^`a opmabypipcœm[ sdáqs>^`chc q c\`aj clh ^]s Øabh3eqabˆ abeq py+itsyp\dc kpch; c\]y+ibibádsd ;\`cly eè[_ˆpcl\ eqajòóc\`chi^ kp\`[p ; 3s ^d py_^#y+\`cm[ph3sdabe;c\`cle YPssd pcœmabclsl VZ3 q^$^d ;cd ;hpeqc\`ijá abh;kôâ[qeqclibs psr 3YPijibáÏeq[ôh;[P^ ;\`[_ˆ abeqc$yqå~cibi eqcoph;cleäsd pcœmaty_^dab[phä clm] py+h;atsr êyy+^d ;cl\l Y{sdc 3YP\`Y+^dab[PhDZc^>å~cch&Y+kPclhI^`s 3sdabh;kÅY$ ; 3ch;[P^>áI 3abmÙ[PZ3sdc\d ˆ_Y_^`aj[ hõabså[+ƒý^dclhõ 3sdcle9 Ó clˆpc\]y+i å [ \dìqsabhõâ[ ijcœm ;ity+\åz;a [Pib[Pk áê 3Y؈ cî ;\d[ p[isrcœehy+hõc q ;ity+hpy_^dab[phh[pƒ sd pcœmaty_^`aj[ hõ\dc ity_^dcœeu^d[êsr^d\`cls`sèï½z{y+^datm+ JyYØáqs`sRabkP 3ajcl\l Lö y YPeq Y+h ŸŒ P u;ø ã YPe;eqcláP z{y_^`abmp pöùyypeq YPh Ÿl P ñ úvypsdcleç[phç^` ;clsdc sr^d 3e abclsl ^d ;atsâ 3Y+ c\ ;\`clsdchi^ YÅsR^d\`cls`s> Z3YPsdcleÎsd clmaty_^`aj[ h) [qeqci Y+hpeÙaj^`sOab ;ibc chi^`y+^dab[phåoaj^d ;abh$xajƒ cl V\d[ û 7 C>/ 8q7 FýüQßW13þvÿ clˆpc\]y+iân\d^dajopmaty+i Xajƒ c)cœm[isráqsr^dc så 3Y؈PcÈZcclh eqcœsrabkph3cle eq ;\`abh;k ^d ;c iby s>^o3ƒý^dcclh$ápcœy+\]s An [Ph;k ^` ;c ãvajcl\d\]y$ï½yyøá Ÿl ;ŸØñ YPh3eDnˆ ate;yîï½nve;y+ a ö ú~\d[_åoh Ÿl ñ YP\dc Z3Y srcœeå[ h [P ; ;ity_^`aj[ h3s[+ƒ sdcijƒý \`c 3\d[qeq 3majh3k)s>^`\dabh;kIsÙåOaj^d 4Y)ã ;\dabh;kp m[ ;ijc^dcok ch;c^datm ZpYPsdabs sd ;Zqë>cŒm ^dcœe ^d[jr[pats`sr[ hq \]Y+hpeq[P4 q ^`Y+^dab[Ph3sl Or[Pibá [ \diteï AY+clkPc\ Ÿl ñ YPh3e LŸ tyï \]YPmabY s ŸŒ P ñ YP\dcV^>å~[+ =eqaj clh3srab[phpy+ióclm[pib[pkpá sdaj ;ity_^d[ \`svsr^d 3e;á abh;kcˆ [Pib q^dab[ph [+ƒm[p pc^dabh;kjy+k chi^`s m[phi^d\`[pibibcleâåoa ^` h;c 3\`YPi h;c^>å [ \dìqsl è VYP\dåOabhJr[Phpeâ｜ chi^d\`cibity Ÿl Pð ñ YPh3e clh;car[ [Pi Y+\`c^>å~[+ =eqabâclh3sdaj[ h3y+iˆ ab\r^` 3Y+iå [ \dite;soåo 3c\`c ; áqsratmsr Z3YPsdcle [P\`k YPh;atsR sl \`clsd pcœm ^`ajˆ cibáômly+ibijcœeéídsdåoaj Zp[P^`s`îÎY+h3eéí`sRåOabâ c\]sdî3 èclˆp[pibˆpc [_ˆ c\l^`aj cp $x3\`yp sr^datm]ì&ïl[p [ sdabh3srì a ž ŽPŽ Ž ñ atswy^d ;\`cc e;aj chpsrab[ph3ypiqijajƒ c sdaj ;ity_^dab[ph ;\`[+ë>cœm ^WåO ;cl\dcoz[+^` ^d 3cV ; áqsdabmly+ipsr^d\` 3m^d ;\`c[+ƒèm\dcœy_^` ;\dcœsayph3e ^d 3cab\~m[PhI^d\`[PisRáqsR ^dcl sy+\`cvclˆp[ ijˆ cle9 nibiê^d 3clsdc sráqsr^dcl s aj ;ibc chi^ p[ ; ;ity_^dab[phps [+ƒty+ ; ^d[ h;[p [ 3s chi^`a ^`ajcœs sd[p c^dabâcœsýsd ;\`clype [_ˆ c\ eqajòcl\dclhi^ sd pcœmabclsl Z3 q^ h;[ h;c#[+ƒv^` ;c ;\`[P [ sdclsy$å~cibi e;co3h;cœeîsr c maty_^`aj[ hhâ[qeqclï -g=htx;\]y+ sr^datm]ìqs abh3eqabˆ abeq py+its{y+\`cèsr 3\dcŒYPe [_ˆPcl\ sd pcœmabclsâeqco3h3cle)y s sdc^]s [Pƒajhpeqajˆ ateq 3YPibs 3Y؈ ajh3kåsrab a ity+\ kpclh;[+^>á clsl ôãv ;c$sd pcœmaty_^`aj[ h&ats h;[+^ Y+hpY+kPcŒeÈZ á)yphiá clm] 3YPh;atsR PZ3 q^ ats ƒ½yøˆ [P\`cleâZ á ib[_å cl\dabh;k^d 3co;^`h;cls`sW[Pƒóh3cå Y+k chi^`sj 3Y؈ ajh;k{sdabâabity+\ k ch;[p^>á pc ^`[{c qats>^`ajh;kå[ph;cœs $r[pibái Q[P\`ibe$YPh3e LŸ ty ;\`[P [ sdcjsrab 3ibY+^dab[Ph3s åo ;c\`cjh;clåhsd clmabcls c cl\dk cp [_å clˆpc\œ ^d ;clá{ 3sdcâY I 3YPijaj^`Y+^dabˆPc e;c^dcl\d abh3y_^`aj[ h Z3Y srcœeä[phä[pz3sdc\`ˆpcœeôzpcl 3Y؈ aj[ \`sl Ug=h LY ty; vyèm[ â c^`a ^`aj[ h Zc^>å~cchç^>å~[ sr clmajcœsvajhåo ;atm] ajh3e;ajˆ ateq 3Y+itsOmYPh Y+^dcL[Ph3ijá åoaj^d Ùabh3eqabˆ abe; 3Y+itsWƒ \`[Pé^` ;clsdypâcvsr clmajcœs pyps ZpclchsR^d peqajcœe Z; q^h3[#sr clmaby+^dab[phçâcœm] 3Y+h3absd 3Y svzpclch ;\`[P [ sdcle9 x; ;h3e3y+ chi^`ypi ;\`abh3mab ;ibcls$[pƒ clˆp[ ij q^`aj[ hõeqá h3y+ atms$ 3Y؈ c ZcchÔc q ;ij[ \dcœeôajhêsdáqs>^`c s Z; ;abij^ùz áä [Ph3\`Y e4ï Ÿl ð ñ YPh3e r YPm]ì_YP\`eçï ŸŒ PðP Iñ QYPkPh;cl\ YPh3e nij^dclhizc\`kï Ÿl u ñ \`c [P\d^`sAY sr^d 3eqá Y+Z[P q^ ^d ;c ídcˆp[ ijˆ_ypz;ajibaj^>á îajhâcˆ [Pib q^dab[ph3yp\dál ;\`[qmcœsdsdclsl r[p 3 ;iby+^dab[phäeqá h3y+ atms#y s \dcœsr 3i ^#[PƒabhI^dc\]YPm^dab[Ph3s Zc^>å~cclh abh3eqabîateq 3YPibsL pyøˆpc ZcclhQsR^d peqajcœe9 èypâ[ h;kç[+^d 3c\]s 9abhQã YØá ij[ \ ï ŸŒ PðP Iñ Oú~cle;YP $ 3YPs ;\`clsdchi^dcœe$y#m[ â py+\`absd[ph$y+hpe$y mityps`sda opmly_^`aj[ h [+ƒócˆ [Pibˆ_Y+Z;ibcOmY+ pypmaj^dabcls [ Zq^`YPajh;cŒeâajh Y+\d^dajopmabYPi clm[ sdáqs>^`c sly+h3e{ƒ \d[ ú~aj[isr ; 3c\`c c qyp ;ijcœs ï½ú~cle;yp Ÿl Pð ø ú~cœe;y+ 3 qhiáqeqcl\l ;ö r YPm]ì_Y+\]e ŸŒ P ð ñ ±_º=º>µ Ä Ä ÄOÑ ÌØ ]¹_º= > ]à à PÑ À]ÁlÂ

2 The environment LifeDrop 1 (Heudin 1999) is a java based virtual ecosystem inhabited by bio inspired creatures. The environment consist of a "virtual water drop" with boundaries acting as "walls" for creatures. It integrates a ž physical engine managing forces using the "steering behaviors" model for autonomous characters (Reynolds 1999). Figure 1. A screenshot of the first version of LifeDrop showing a small set of creatures moving in the 3D environment. x ajk ;\`c Ÿ98 n sdm\dclch3sd ;[P^L[Pƒv^d ;c op\`sr^ ˆPcl\`sdab[PhQ[+ƒXajƒ cl V\d[ sd ;[_åoajh3k Y sd Y+ibièsRc^[+ƒ m\`cly+^d ;\`cls~ [_ˆ ajh;k abhç^d ;c: õch ˆ aj \`[Ph; chi^œ The environment includes several parameters such as water fluidity, acidity, etc. The ph parameter ranges from 0.0 (no creature can live) to 1.0 (no impact). It simulates the chemical impact G :<;]7>= of13ß@?ba the number < 7 1 of <:>7living ü creature in a closed environment. CEDGFFIHJGKMLON5HQPFRHS Xajƒ cl V\`[P TabsYÅëRY؈_Y_ Z3YPsdcleäˆ ab\r^` 3Y+iLclm[ sdáqs>^`c The creatures ajh3 3Y+Z;aj^dcŒe Z áz3aj[p abh3sd ;aj\`clem\dcœy_^d 3\dcŒs ~ãv ;cjch ˆ ab\d[ h; chi^m[phpsrats>^v[+ƒ Y Each creature is an autonomous agent that can be írˆ ab\r^` 3Y+i åvy_^dcl\e;\d[ 3îÙåOaj^d Zp[ ;h3e;yp\dabclsly m ^dabh;kçypsçíråvy+ibibs`î described by a layered hierarchical model (Heudin 1998a) ƒ [P\$m\dcŒY_^d 3\dcŒs g ^$abh ^`ck \`Y+^dclsçY& ; á sdatmy+ich3kpabh;c YPh3Y+kP abh;kçƒ [P\]mclsL psrabh;kç^d ;cîí`s>^`ccl\dabh;kçzpcl 3Y؈ aj[ \`s`î# [qeqciwƒ [P\JY+ ; 1 LifeDrop can be experimented on line on the following web site at ^d[ h;[p [ 3sOm] 3Y+\]YPm^dcl\`sï½yOclá h;[pite;s worlds.net/lifedrop. Ÿl P Iñ ãv ;cjch ˆ ab\d[ h; chi^ abh3mib 3eqcŒs sdcˆpcl\`ypi 3YP\`YPâc^dcl\`ssd 3m] {Y s åvy_^dcl\vu3 ;ateqaj^>áp Y mateqa ^>á Oc^]m+ Tãv ;cxwzy 3YP\`YPâc^dcl\#\`YPh;kPcŒs ƒ \`[PÓŽ; Ž)ï½h;[Dm\`clY_^` ;\`cmyphèibajˆ c ñ ^d[ Ÿ Ž)ï h3[ab 3YPm^ ñ )g ^ sdaj ;iby+^dcœs ^` ;cm] ;c atmy+ivab 3YPm^â[Pƒ^d ;cçh ; Zc\ [Pƒ ijabˆ ajh3k m\`cly+^d ;\`cajh$y mib[ sdclech ˆ aj\`[ph3âclhi^l CEDGF[ZLOF]\)SO^GLOF]_ æay m] Qm\dcŒY_^` ;\dc atsjy+hîyp q^d[ h;[p [P psy+kpclhi^^` 3Y_^âmY+hDZc#eqc s`m\`ajzclelz áyoityøápc\`cle ;abc\]y+\]m] ;atmypi+ [ e;cipï cl 3eqabh Ÿl PðIñ ajhq sd ;aj\`cleƒ \d[ U^` ;cvsr ;ZpsR ; q^`aj[ h Y+\]m] ;aj^dcœm ^d 3\dcï½ú~\d[ [ ì s Ÿl ;ŸŒñ g=hç^d ;ats [qeqclï Y k ajˆ chibcˆpcli\`cibajcœsv[phç^d ;c c qabsr^dclh3mc[pƒ aj^`s sd ;Zq ijclˆpcitswyph3e#y+ibi3ibcˆ citsayp\dcoabhi^d\`ajh3sdatmy+ibibá 3YP\`YPijibci V ;\`ajh3k YmáqmibcP _cœypm] JitYØáPcl\\`clmcabˆPclsabhqƒ [P\` Y_^dab[PhJƒ \d[ H^d ;cvch ˆ ab\d[ hq chi^vyph3esrclijcœm ^`s Y+h$YPm^dab[Phç^d[ Zcc qclm q^dcœe9 vãv ;cjm ;\`\`chi^ [qeqciab ;ibc chi^`soo3ˆpclityøápc\]s 8 Èa b5cp ed)fgaig ^` ;c ídeqabkpaj^`ypi ihvn î [+ƒ ^d ;c m\dcœy_^d 3\dc z$c^]y+z[pibabsd 8 Y+h3YPkPclsè^d 3c cœsdsdchi^daty+i máqmijcœsibabìpcaibajƒ c^dab cp j Ç3²ÆÉt ]Ê~ >ÁlµÀ] l¹å¼q *kpµq ` >²  ]¹_º> ¾Ál¹»½Ã ² ¹I ÁŒ¹$º>±I JÉtÁlà à Á ÄW² ¹IÐ Ä `¼ ³=²Æº> ºA±_º=º>µ] Ä Ä ÄOÑ Ì+²Æ =º>Í ÃÆ»½Ä Ál >à ¾ ³]Ñ ¹ `º7à ²ÆÉt ¾+ >ÁŒµ3Ñ simulating the impact of the "physical conditions" such as water fluidity, ph, etc. Reactive behaviors: manages basic reactive behaviors, such as obstacle avoidance, fleeing, etc. Cognitive behaviors: manages behaviors such as the selection of a mating partner.!#"$&%')(*%,+-/./% Creature genotype Each creature is characterized by a genotype that determines eqcˆ cib[p ; chi^y+hpeùk \d[_åv^` q Y_^dabh;kp qc^`mp most of its morphological and behavioral parameters. It is composed of 4 "chromosomes", each of them containing 8 "genes". Figure 2 gives the mapping of these encoded parameters. l d/b Zmon½ P«pg YPh3Y+k cls ^d ;c m\`cly+^d ;\`cpf s#ídajhpmy+\`h3y+^dab[ph3î#sdab ;iby+^dabh;k$^` ;c#abâ pypm ^ [+ƒv^d ;c&ír ; áqsdabmly+iwm[ h3eqaj^dab[ph3s`î$sd 3m] YPsvåvY_^dcl\QU3 ;ateqa ^>á qwzy qc^]m+ Chromosome #0 Meta genes Gene #0: Number of chromosomes in the genotype. Gene #1: Matching level with another genotype. Gene #2: Mutation level. Gene aj[ \`sl ;sr pm] çy sv[pz3sr^`y mibclyøˆ [Pate;Y+hpmcP pu3clcabh;k3 qc^`m+ #3: Internal clock: lifetime in cycles. Gene #4: Internal clock: cycle time. Gene #5: Maximum energy level. Gene #6: Maximum number of children per reproduction. Gene #7: Unused. r a ; P n&s]a$ªga t 9s/nc3 _«pg YPh3Y+k cls&z3ypsdabmu\`clypm^dabˆpcuzpcl 3YØÎ uvc]wibn n&s]aªga t 9s/nc3 _«pg YPh3Y+k clsvzpcl 3Y؈ aj[ \`svsr 3m] QYPsV^d 3c srclijcœm ^dab[phç[+ƒ Yâ Y_^dabh;k 3YP\R^`h;c\Œ Chromosome #1 Structural genes Gene #0: Recursion order for development. Gene #1: Segmented or not (Dawkins 1988). Gene #2: Number of segments if segmented (Dawkins 1988). Gene #3: Delta parameter for segmentation (Dawkins 1988). Gene #4: Gradient parameter for segmentation (Dawkins 1988). Gene #5: Jaws force level. Gene #6: Color. Gene #7: Unused. x LOF]\/Sp^GLOFoy5FIHzN/S{@ #F æay m] &m\dcœy_^d 3\dcçabsÙm] 3Y+\]YPm^dc\`a}cleÈZIá&Yk ch;[p^>á pcç^d py_^#eqc ^dcl\d abh;clsâ [ sr^ [Pƒ aj^`sâ [P\` ; ;[Pib[Pk abmly+i~y+h3e)zpcl 3Y؈ aj[ \`YPiA 3Y+ \]Y+ c^`c\]s çg ^ ats m[ p[isrcœed[+ƒo Ôídm] ;\`[P [IsR[ âcœsdî3 cly m] D[+ƒ ^d 3c m[phi^]y+abh;ajh3k ð írkpclh;cls`î; ~x ajk ;\dc ž kpabˆpcls~^` ;cj Y+ 3 ;ajh3k [+ƒ ^d 3clsdcclh3m[qeqcŒeç 3Y+\]Y+ c^`c\]s Chromosome #2 Morphological genes Gene #0: dx #3 parameter (Dawkins 1988). Gene g=hùype;e;a ^`aj[ h ^d[^` ;clsdc 3YP\`YPâc^dcl\`sl PcŒYPm] m\`cly+^d ;\`cokpc^`sayph #1: dx #4 parameter (Dawkins 1988). Gene #2: dx #5 parameter (Dawkins 1988). YPe3eqa ^`aj[ h3y+iwsdc^j[pƒ~ py+\]y+ c^`c\]sy+ƒý^dcl\ja ^]sjeqclˆpcib[p 3âclhI^L 3\d[P Gene #3: dy #2 parameter (Dawkins 1988). mcœsdsl )ãv ;cœsrcabh3mib 3eqc YPâ[ h;kq[+^d 3c\]s ^` ;cäídypijabˆpcœî; ír ;h; Gene #4: dy #3 parameter (Dawkins 1988). Gene #5: dy #4 parameter (Dawkins 1988). kp\`áqî; #írƒ clm ;h3e;î&y+h3eýídsr^d\`cls`srcœe;îîs>^]y_^`clsl énvsçå cåoajibisrclc Gene #6: dy #5 parameter (Dawkins 1988). ity_^dcl\l v^` ;cêí`s>^`\dcœsdsdcle;îîsr^`y+^dc{ pyps#yèe;aj\`clm^ùaj 3Y m ^ç[phä^d 3c Gene #7: dy #6 parameter (Dawkins 1988). m\`cly+^d ;\`cpf slzc 3Y؈ ab[p\]sy+h3edy+itsd[$[phq^d ;csr clmaby+^dab[phd clm] 3Y+ Chromosome #3 Behavioral genes h;atsr Gene #0: Number of creatures which can be perceived. Gene #1: Maximum radius for perception. Gene #2: Recognition rate. x Gene LOF]\/Sp^GLOF~PN>LO DGN N5y/{ \>Hzƒ #FIDz\]JGKN5Lp_ #3: Mating behavior weight. Gene #4: Eating behavior weight. Gene #5: Fleeing behavior weight. ãv ;cè [ \d ; 3[Pib[PkPáÏ[+ƒ#Xajƒ cl V\d[ f Gene #6: Flocking behavior weight. såm\`cly+^d ;\`clsåvyps{ajh3sd ;ab\dcœe Z á$^d 3c å [ \dìqseq[ph;c Z áåyoatm] 3YP\`eQ VYØåOì abh3såoa ^` Q^d ;c Gene #7: Render behavior weight. ˆ ŠIŒ Ž* q Figure $ï½ YØåOìIabh3s 2. The encoded ŸŒ Pð parameters ;ø Ÿl ðp ñ ~ Ôaj^d 3ajhêXèa ƒ cœ \`[P in the genotype. ^d 3clsdc ž &sr 3YP pcœsmypijibcleí`ú~aj[ â[ \d 3 3sdî3 3Y؈ c Zpclchc ^`ch3eqcœe ^d[y+ q^`[ph;[ â[ 3sJYPkPchI^]s m] 3YP\`Y m ^dcl\da}cœeåz á :P sr 3YP pcœs YPh3e sd ;[_åoajh3kây ˆ_Y+\`abc^>á [+ƒzc 3Y؈ ab[p\]s æaypm] Y+k chi^w 3Y s a ^]sw[_åohâcibc chi^]y+\`á c\]mc ;^dab[ph sráqsr^dclç g ^ pcl\`mcabˆpclsy+ibi [P^d ;cl\ m\dcœy_^` ;\dcœsèmij[isrc ch;[ ;kp abh YÙíR c\]mc ; ^dab[ph{sd ; ;cl\dcœîâåo ;abm] $ YPajh 3YP\`YPâc^dcl\`sOYP\dcLchpm[qeqcleabh^d 3c ƒ [P 3\R^` Qm] ;\`[P [IsR[ âc J cl pclh3eqabh;k[ph^d ;cœsrc sdch3sd[p\`áajh;ƒ [P\d Y_^`aj[ hçyph3eùaj^`sajhi^dcl\dhpy+isr^`y_^`cp ;YPhçYPkPchI^sdcibclm ^]soy+hypm^dab[ph abh#^d 3csdc^v[+ƒè [ s`sdajz;ibc Zc pyøîab[p\]say+^~cœypm] Ùsdab ;ity_^`aj[ hùmáqmibcp æ ;YPâ 3ijcŒs [PƒW p[isdsdajz3ijc Zpcl 3Y؈ aj[ \`sy+\`c^d 3c ƒ [ ijib[_åoajh3k 8 ib[i[ ìi abh;k ƒ [P\V Y_^dc 3ib[ [Pì ajh3k ƒ [P\ƒ [ [qe9 ]U3cclajh3kÙY#e;YPh;kPcl\l ; [_ˆ abh;k \]Y+h3eq[ ijá U3[qm]ìIabh;kp Ic^`mP nibiypkpchi^]s#abh ^`c\]ypm^ùajhê^d ;cqsdypâcåîab\d^d 3YPiVeq\`[P Ô[PƒJå~Y+ In addition to these parameters, each creature gets an additional set of parameters after its development process. ^dcl\\dcœsr ;ij^dabh;kôajh4y&m[p ;ibc ï½clm[p ñ sráqsr^dclç ãv 3c\`cÅatsh3[ c q ;ibatmaj^ùo;^`h;cls`sƒ ;h3m ^`aj[ hê[p\y+h áôkpib[pz3ypivsdcibclm^dab[phê ;\`[qmc eq ;\`cp ãv ;clsd 3mmcls`sW[+ƒ sr[ âcv ; ;clh;[+^>á cls c c\`kpcœs ƒ \`[Pé^d 3c abh ^`c\]ypm^dab[ph3szc^>å~cclhèy+k chi^`s ajhd^` ;cùclhiˆ ab\d[ h; chi^l { [ c Y+k chi^`sùsr ;[_å YDkP[ [qeäype;yp q^`y+^dab[phäåo ;abijcqsr[ c$[+^d 3c\]s#eqabc I ;aj^dcâ\`yp ;abe;ijáîï ì abijibcleåz áç[p^d ;cl\`s ƒ [P\c ;YPâ 3ijc ñ ãv 3s 9YPhIá abh3eqabîateq 3YPiLZp[ \dhuajh; 3c\`a ^]sùk ch;cœs#^` 3Y_^$ 3Y؈ cåsr pmmclcleqcœeêabh Z; ;abiteqajh3k Y sdc\`ajcœs~[+ƒ sd 3mlmcls`sRƒ ;i9 ; ;clh;[+^>á clsl g=h^d 3abssdchpsRc å~câmly+håsr^`y+^dc ^d 3Y+^LXèa ƒ cœ \`[P aj ;ibc chi^]s ^` ;câ ;\dabh3maj ;ibcâ[+ƒ h3y+^d ;\]Y+isdcibclm^dab[Ph

3 n $ + ) 9%, 7š) ]!œœ9+ * #1žÕ+qŸ 1ž p < : ;\`[P [ sd[p c Ž z$c^`y k ch;cœs clh;c Ž 8 h ; Zc\ [+ƒm] ;\`[P [ sd[p cœsvabhd^d 3c#kPclh;[+ ^>á cp clh;c Ÿp8 zåy_^`m] 3ajh;kibcˆ cipåoa ^` #Y+h;[P^d ;cl\akpclh;[+^>á cp clh;c žz8 z{ q^`y+^dab[phijclˆpclï clh;c : 8 g=hi^`c\`h3y+imij[qm]ì 8 ijajƒ c^`aj cabhmáqmibclsl clh;c J 8 g=hi^`c\`h3y+imij[qm]ì 8 máqmibc^dabâc clh;c u 8 zåy_ qaj ; clh;c\`kpá#ibcˆ ci clh;c 8 zåy_ qaj ;-hi 3 Zc\â[+ƒ m] ;abibe;\dclhî pcl\ \`c 3\d[qeq 3m^dab[Ph clh;c â 8 w h 3sRcŒe9 3\d[ â[isr[ c Ÿ I^`\d 3m^d ;\]Y+i9k ch;cœs clh;c Ž 8 yclm 3\`sdaj[ h[ \`e;c\~ƒ [P\eqclˆPclij[ ; chi^l clh;c Ÿp8 qckp clh ^`cle[p\oh;[p^ ï½ YØåOì ajh3s ŸŒ Pð ð ñ clh;c žz8 h ; Zc\ [+ƒ srclkp chi^]s a ƒ sdck âclhi^dcle ï VYØåOì abh3s Ÿl ðpðiñ clh;c : 8 Vcij^`Y6 3YP\`YPâc^dcl\ ƒ [P\ sdckp clh ^]Y_^`aj[ h ï VYØåOì abh3s Ÿl ðpðiñ clh;c J 8 \]YPe;ajclh ^ 3Y+\]Y+ c^`c\ ƒ [ \sdckp clh ^]Y_^`aj[ h ï VYØåOì abh3s Ÿl ðpðiñ clh;c u 8 IYØås ƒ [P\]mcLibcˆPclï clh;c 8 [ ij[ \l clh;c â 8 w h 3sRcŒe9 ;\`[P [ sd[p c ž z$[p\` ; ;[ ij[ kpatmy+ikpclh;cls clh;c Ž 8 eq X v: 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c Ÿp8 eq X 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c žz8 eq X âuâ 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c : 8 e;áe ž 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c J 8 e;áe v: 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c u 8 e;áe 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c 8 e;áe âuâ 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ clh;c â 8 e;áe 3Y+\]Y+ c^`c\ï½ YØåOì ajhps Ÿl Pð ð ñ ;\`[P [ sd[p c v: ú~cl 3Y؈ aj[ \`YPipk ch;cœs clh;c Ž 8 h ; Zc\ [Pƒm\dcŒY_^d 3\dcŒsèåO ;atm] my+hâzc~ c\d mcabˆpcœe9 clh;c Ÿp8 zåy_ qaj ; \]YPeqab 3s~ƒ [ \O pcl\`mc q^`aj[ h clh;c žz8 yclm[ kph;aj^dab[phç\]y_^dc clh;c : 8 zåy_^dabh;k Zc 3Y؈ ab[p\vå clajk I^l clh;c J 8 æ Y_^`ajh;k Zc 3Y؈ ab[p\vå~cabkp I^l clh;c u 8 x ibcclajh;k Zc 3Y؈ ab[p\oå~cabkp I^l clh;c 8 x ib[qm]ìiabh;k Zc 3Y؈ ab[p\vå clajk I^l clh;c â 8 ych3eqcl\ozpcl 3Y؈ aj[ \vå clajk ^Œ x abkp ;\`c žq8 ãv ;clchpm[qeqcleç 3YP\`YP c^dcl\`s~abhç^d ;ck ch;[p^>ái cp F? 7 2 : / 7 C 7ª 8 ÿ ÿpn«v/ ÿ 8;: ßAM.0ßOF KMN5 MN>yK[\> K HG_ KMLp\/SpKMN5H ãv ;c [ sr^åoabeqclijáqypmlmc ;^dcleqeqco3h;aj^dab[phq[+ƒoysd pcœmabclsats^d 3c [Ph3c ;\`[P [ sdcle Z ájæw\`h3s>^ z{yøá \vï Ÿl ð ž ñ coeqco3h3clsyvsd clmabcls YPs~YJsdc^~[+ƒèabh3eqabˆ abeq py+itsw^` 3Y_^âídmYPh Y_^dcLY+hpe Zpc ƒ clm ;h3e#zc ^>å~cchù^d ;cl 3Y+h3eÙ[Ph;ibá Zc^>å~cch^d 3c î; A pm] Y eqcoph;a ^`aj[ h Creature morphology and behaviors The morphology of LifeDrop s creatures was inspired by the works done by Richard Dawkins with the Blind Watchmaker (Dawkins 1986) (Dawkins 1988). Within LifeDrop, these 2D shapes called "Biomorphs", have been extended to autonomous agents characterized by 3D shapes and showing a variety of behaviors. x ajk ;\`c : 8 æ ;Y+ ;ibcls [+ƒ Z;ab[P [P\` ; 3slfÏsd 3Y+ cls ï½y+ƒý^dc\ Figure 3. Examples of biomorphs shapes (after Dawkins). YØåOìIabh3s ñ Each agent has its own elementary perception system. It perceives all other creatures close enough in a "perception abâ 3ijatmaj^dibá&abh ˆP[ ijˆ cls Y4ídsd pcœmabcls ZpY+\`\dabc\]îÅ 3\dabh3mab ;ibcp våo ;atm] sphere" which main parameters are encoded in the fourth ;\`cˆ chi^`sa\dcl ;\d[qeq pm ^dab[ph Zc^>å~cclh ^>å~[jajhpeqajˆ ateq 3YPibsAƒ \d[ chromosome. Depending on these sensory information eqa ƒý ƒ c\`chi^sd pcœmabclsl and its internal state, an agent selects an action in the set ofyoclmchi^dibáp z{y_^`abm Y+hpeÅ ;atsm[ ijibclypkp ;cœs 3Y؈Pcâ ;\`[P [ sdcleåyph possible behaviors at each simulation cycle. Examples c q ;ity+hpy_^dab[ph[+ƒ ^d ;c sd pcœmabclsƒ [P\` Y_^`aj[ hy_^ [Pibclm ;ity+\sdmly+ibc of possible behaviors are the following: looking for mate, ƒ [P\AZ3YPm^dc\`atY ï½z{y+^datm+ yyøáqsdsdajk ;abc\œ +ö4y YPeq Y+h looking for food, fleeing a danger, movingÿœ P randomly, u ñ ãv ;abs sr^d 3eqáôsR 3[_åsâ^d 3Y+^#^d ;c{sd clmabcls#z3y+\`\dabc\ ats Y+abhI^`YPajh;cŒe)Z á flocking, etc. kpclh;clsm[ h ^`\d[ ijibabh;kîyî absd Y_^`m] Ô\`c py+ab\dabh;kèsdá sr^dcl ï z{y All agents interact in the same virtual drop of waterñ [+ƒv ihvnj 9g=hDYPe;e;a ^`aj[ hå^`[aj^`sl\`c 3YPaj\`abh;kÙ ;\`[P c\d^>áp ó^` ;atssráqsr resulting in a complex (eco )system. There is no explicit ^dcl0å~yp\d\]y+hi^]s^d 3Y+^ fitness function or any ^>å~[{kpclh;[+^>á cls global selection åoa ^` Î^d[ [ ;ajk )eqajòcl\r procedure. The success of some phenotypes emerges from the interactions chpmcls my+h3h;[+^ \`clm[p Z;ajh3cZc^>å~cclh^d ;cl vãv 3sl 3åO 3ch^d 3c between agents in the environment. Some agents show a z{y good ats YPm^dabˆPcP P[Ph;ibáJabh3eqabÎateq 3YPibs pyøîabh;klsrab ajity+\ k ch;[p^>á pcœs adaptation while some others die quite rapidly Y+\`cJƒ cœm ;hpe{zc^>å~cch{^d ;cl (killed by others for example). Y+h3eÅåOajibiZc Y+Z;ibc Thus, any individual ^`[Ù Y_^`câsd 3m born mcœsdsrƒ ;ibijá 4 [_å clˆpcl\l a ƒl^d 3cÅz{y ôk ch;cœs Y+\`c$ajh3Y m ^`ajˆ_y_^`cle9 inherits genes that have succeeded in building a series of ^d 3cVsd pcœmabcls Z3Y+\`\dabc\ Zclm[P cls å~cly+ì Y+hpe ajh3e;ajˆ ateq 3Y+its~eq[Jh;[P^ successful phenotypes. In this sense, we can state that LifeDrop implements the principle of natural selection. h;clcle$y+h á [P\`cL^d[# pyøˆpcj 3m] $kpclh;c^`abm 3\d[Ø qabâaj^>á#^`[#zcjƒ c m 3h3eQZpc^>å clchq^d ;cl Ùz$[P\`c[_ˆ c\œ óajhîsd 3m] QYmlYPsdcP ^` ;c [PZ; sdc\`ˆpcleù q^]y_^`aj[ h3y+i9\]y_^`czclm[p clsˆpc\`á ;abkp ìpcláqƒ cly_^` ;\`c#[+ƒo^` ;abs sr^d 3e;áQats The Stress based Speciation ^d 3Y+^ abh; ;abz;a ^`aj[ h)[qmm ;\]s Model ƒ [P\Åajh3e;ajˆ ateq 3Y+its{sR^d\`cls`sRcŒe4ZIáÏ^d ;claj\åch ˆ aj\`[ph; clh ^Œ Ô ;clh abh3eqabîateq 3YPibs Y+\`c#s>^`\dcŒsdsdcleQZ ádeqa #m ;i ^âch ˆ aj\`[ph3âclhi^`y+i m[ph; Biological inspiration eqaj^dab[ph3sl ^d ;cláqmly+hd\dcl ;\`[ e; 3mc åoaj^d Îabh3eqabˆ abeq py+its^d py_^l abhîy The most widely accepted definition of a is the h;[ hq sr^d\`cls`sdclesraj^d 3Y+^dab[Ph Øå~[P ;itezpc m[phpsrateqc\`clevƒ \`[P4Y+h;[P^d ;cl\ one proposed by Ernst Mayr (Mayr 1982). He defines a sd pcœmabclsl nve;eqabh;kl^d ;c~ƒ½y m ^ ^d py_^ ^d 3cO as a set of individuals that q^]y_^dab[phpy+iq\]y_^dc~ats^d ;clh "can mate and be ;abkp ;cl\l _sr^d\`cls`srcœelsr clmajcœsèk [O^d ;\`[P 3kP JeqabˆPcl\`sda omy_^`aj[ h / Ô ;clh fecund between them, and only between them". Such a ^d 3cJs>^`\dcŒsdsOeqcŒm\`clY srcœs I^d 3cJsR clmajcœsvz3y+\`\dabc\vatsv\dcœs>^`[p\`cle9 ± N²ƒzFR K P MFIPFIHSp\)SpKMN5H æay m] UXèa ƒ cœ \`[P HY+k chi^$abs$m] 3YP\`Y m ^`c\`a}lcleôz áuyô 3YP\`YP c^dcl\ h3ypâcœë Že ˆ Š ³3 åo ;abm] atsochpm[qeqcleçabh$a ^]soo3\]sr^ m] ;\d[p [ sd[p cï m ƒ> ÎopkP ;\`c ž ñ Èãv ;atsâ 3Y+\]Y+ c^dc\â\`c ;\`clsdchi^`s ^d 3c ajh3aj ; ídkpch3c^datm ;\d[ø qab a ^>áqîˆ_ypij ;c~^` ;abswajh3e;ajˆ ateq 3Y+iq 3sR^ 3Y؈ cååoaj^d UYPh;[+^` ;c\^d[&zpcdy+z3ijc^d[&\dcl ;\d[qeq pmcp ùg ^{srab ; ity_^dcœs^` ;c s>^`\d pm ^d 3\`YPi m[p 3Y_^`ajZ3ajiba ^>ázc^>å~cclh{^>å~[eqajòcl\dclhi^ kpclh;[+^>á clsl n sy m[ h3sdcl I ;chpmcp ^` ;cjeqco3h;aj^dab[ph[+ƒyâsd clmabcls ats 8 µ/ G ˆ ŠIŒˆ ˆ&Œ¹»º¼ 7¼Ž ŠZº½ˆ&Œ 7 Œ 6¾ Z º º WeŽ ˆ º ˆ ¾ Z ˆ ³ Š À*W ˆ Ž#WI Á ˆ ˆ MÀ ˆ,ºÂ³ 7 Š Ž* <¾ Z ˆ 7 º WZeŽ ˆ à Že ˆ ŠO³ ¹ º ãv ;cvk ch;[p^>á ;abm ;\d[ø qab a ^>ávä5å Å T abs kpabˆpclh#z á ^` ;cc q ;\`clsr explana for bac study sh genes co DNA. 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5 u cycle. lso acts uations, and its duction values, onstants riments he first pes and ing the ulations s the ph certain ecomes low one l initial en) and during ses, this ever, in portant r 20,000 er been a first phase and then stays relatively constant. The average stress of the creatures varies a lot during the first steps of simulation and then tends to stabilize itself as for the population. In all experiments of this type, the stable state corresponds to low number of, usually ranged between 5 and 10. In any cases, the number stay strictly greater than one, which means that different co evolve permanently in the environment. Figure 5 shows the time series for a typical experiment with an initial set of 100 creatures. $ + ) 9%, 7š) ]!œœ9+ * #1žÕ+qŸ 1ž p < x ajk ;\`c u 8 ãvab c#srcl\dabcls[pƒ [P ; ;ity_^`aj[ h h ; Zpcl\[+ƒ~sd clmabcls ï Z[+^` [Phç^d ;cibcƒý^ Y+ qabs ñ Y+h3eçY؈Pcl\`YPkPcVsR^d\`cls`sï \`abkp I^Y_ qabs ñ Figure 5. Time series of population, number of (both on the left axis) and average stress (right axis). Experiments with crisis All experiments of the second type show the same dynamics as in the first type with the exception of crisis periods. During these periods, the ph is forced to 0.5. This has the effect to reduce by half the lifetime of the creatures and to force their stress rate up to 0.5, which rarely appears in normal simulations. Figure 6. Time series of population, number of (both on the left axis) and average stress (right axis). x ajk ;\`c 8 ãvab c#srcl\dabcls[pƒ [P ; ;ity_^`aj[ h h ; Zpcl\[+ƒ~sd clmabcls ï Z[+^` [Phç^d ;cibcƒý^ Y+ qabs ñ Y+h3eçY؈Pcl\`YPkPcVsR^d\`cls`sï \`abkp I^Y_ qabs ñ As a result, the number of decreases when the crisis begins. This is a consequence of two facts. First, a high number of individuals die, which may cause the disappearance of a number of. Then the barriers become low due to the high value of stress. Thus, surviving agents are distributed among few. Despite the lowness of the barriers, the number of increases slowly during^d 3c the m\`atsratsats ˆ c\`áù ;abkp è x ajk ;\dc crisis. The stress rates having quite no variation, this means that newborn creatures present a high variability, enough to be considered as belonging to different than the already present ãv ;c^d ;ab\]e)^>á c{[+ƒlc q c\`aj clh ^]s sr 3[_åsâ^d ;ats#zc 3Y؈ ab[p\]s one. It is well showed at the end of the crisis. When the ph returns to a opkp ;\`cd "normal" ñ Ô ;ch4yèsrab value, the 3ibY+^dab[PhêZck ajh3s number strongly increases, showing that the diversity between individuals issued from the crisis is very high. Figure 6 shows results for a typical experiment of this kind with 100 initial randomized genotypes. ;\`clsdchi^ùyd ;abkp äˆ_y+\`abypz;abijaj^>áp vch3[p ;k &^`[ÎZpcm[PhpsRateqc\`cleäY s Zcib[Ph;k ajh;kå^d[qeqa òóc\`chi^ sr clmajcœsj^` 3Y+hÎ^` ;cy+ib\dcœypeqáq ;\`clsdchi^ [Ph3cP Qg ^âats å~cibivsr ;[_å~cle)y_^ ^` ;cçch3e)[+ƒo^d 3cçm\datsRatsl Ô ;clh ^d 3c p H\dc^d ;\`h3s ^d[ YQíRh;[ \d Y+itîJˆ_YPij ;c ^d ;csd pcœmabcls~h ; Zc\ sr^d\`[ph;k ijáèabh3m\dcœypsdclsl AsR 3[_åOajh;kQ^` 3Y_^ ^` ;c{eqabˆpc\]sda ^>áèzc^>å~cclh abh3eqabîateq 3YPibsVatsdsd ;cleçƒ \`[P sd ;[_åso\`clsd ;i ^]sƒ [ \VY ^>á ;atmypièc c\`abâclhi^ [+ƒ ^` ;absvì ajhpe$åoa ^` Ÿ Ž Ž abh;aj^daty+i\]y+hpeq[p a}clekpclh;[+^>á clsl sr^dabijilzc^r^`c\dï½mƒ> åoaj^d &YQsdc^ [+ƒvm\dcœy_^d 3\dcŒsJ 3Y؈ abh;k{^` ;cçs`y+ ckpch3[+^>á pc ^d 3c h ; Zc\ [PƒVsR clmajcœsâajh3m\dcœypsdcls srib[_åoijádclˆpch&zpcƒ [P\`cYQm\`absdats c\`aj[qedatsjƒ [ \`mcleqz áå^` ;cù 3sdc\Œ {ãv ;cùsr^d\`cls`sjatsj\]y_^` ;c\ ;ajk eq ;\`abh;kâyâib[ph;kâ c\`aj[qeùy+^v^d ;clzckpabh;h;abh;k [+ƒè^d ;cjsdaj ;ity_^dab[phè Y+\`[P 3h3e Ž3 p PåO ;atm] YØáJZpc ;h3eqcl\`sr^d[ [qe YPs ^d 3cajh3a ^`abypipm\`cly+ ^d 3\dcŒs å~c\`cùh3[+^ å clijioype3y+ q^`cleî^`[å^` ;cab\ ch ˆ aj\`[ph3âclhi^l Èn s Y\`clYPm^dab[Ph è p[ ; ;ity_^dab[phîk [ cls^d 3\d[ ;kp DeqabˆPc\]sda opmly_^`aj[ hqyph3e h;clå sd pcœmabcls Y+ ; clyp\l &ãv ;absâats⃠[Pibij[_å~cleÈZIá&YeqcŒm\`clY src[+ƒ ^d 3cY؈Pcl\`YPkPc sr^d\`cls`s ÅXY_^`c\Œ Y+ƒÝ^dcl\ Y{m\datsRatsJ c\`ab[ e ^d ;cçeqa ˆPcl\`sdaj^>áJ 3YPsAZpcŒm[ âcoclˆpclh â[ \dcoab p[ \R^]Y+hI^AY+hpeâ^d ;c sdáqs>^`c sr^`y+z3ajiba}lclsl IY sasdcclh ajh op\`sr^a^>á cvsdaj ;iby+^dab[ph çh[p^dc ^d 3Y+^A^d 3c ZckPabh;h;abh;k{[Pƒv^d ;cœsrcc q pcl\dab chi^`sjabs \`Y+^d ;cl\ eqajòcl\dclhi^j^d 3YPh increases slowly during the crisis. The stress rates having quite no variation, this means that newborn creatures present a high variability, enough to be considered as belonging to different than the already present one. It is well showed at the end of the crisis. When the ph returns to a "normal" value, the number strongly increases, showing that the diversity between individuals issued from the crisis is very high. Figure 6 shows results for a typical experiment of this kind with 100 initial randomized genotypes. Figure 7. Time series of population, number of (both on the left axis) and average stress (right axis). x ajk ;\`c# 8 ãvab c#srcl\dabcls[pƒ [P ; ;ity_^`aj[ h h ; Zpcl\[+ƒ~sd clmabcls ï Z[+^` [Phç^d ;cibcƒý^ Y+ qabs ñ Y+h3eçY؈Pcl\`YPkPcVsR^d\`cls`sï \`abkp I^Y_ qabs ñ The third type of experiments shows this behaviors still better (cf. figure 7). When a simulation begins with a set ofappear. creatures Thishaving followed the same by genotype, a decreasethe of number the average of stress. increases Later, after slowly a crisis even before period, athe crisis diversity period has is forced become byeven the user. morethe important stress isand rather system high during stabilizes, a longas period seen inat first the type beginning simulation. of thenote simulation, that the around beginning 0.4, of which thesemay experiments be understood is rather as the different initial than creatures previous wereones. not well As aadapted matter tof their fact, =Ï: ÿ 29E ÿ ÿ environment. all creatures : ßAM having As a reaction, the same population genotype, goes population throughextinction diversification is more and frequent. new The "success" of an experiment is thus highly dependent on the chosen genotype. ;\`cˆ ab[p 3sO[ h;clsl n sy Y_^d^dcl\ [+ƒƒ½y m ^l óy+ibim\dcœy_^` ;\dcœso 3Y؈ abh;k ^d 3cÅsdYP cçk ch;[p^>á pc ~ [P 3 ;iby+^dab[phäc ^`ajh3m^dab[phäats [P\`cƒ \dc I ;chi^œ ôãv ;cäí`sr 3mlmcŒsds`îÅ[PƒYPh)c q c\`aj clh ^ atsâ^d 3s ;abkp 3ijá eqcl pclh3eqchi^[ h^` ;cjm] ;[IsRclhÙkPclh;[+^>á cp yocœsr ;ij^`svsr 3[_å cœe#^` 3Y_^ abhôírh3[p\` YPibî sda ^` 3Y_^`aj[ h3sv^` ;c [P ; 3ibY+ ^dab[phè Ø^d ;cvsr clmajcœs hi 3 Zc\Y+h3eJ^d ;c~ cly+h s>^`\dcœsdsè^dclh3e^`[sr^`y+ Z;abija}c [_ˆPc\^` ;co^`aj cp ãv ;c cˆp[ ij ;^dab[phâijcœype;s^`[ YL [P ; ;ity_^`aj[ h m[ p[isrcœe[pƒoajh3e;ajˆ ateq 3Y+itsJå~cibi Y e;y+ ;^dcleq^`[$^d 3cab\ ch ˆ ab\d[ hq chi^sr ;\`cly e[_ˆpcl\vy ƒ clåth ; Discussion Zc\L[PƒAsR clmajcœs Ô ;clhåch ˆ aj \`[Ph; chi^]y+ieqa #m ;ij^dabclsyp ; cly+\œ q\`clsd ;i ^]sosr 3[_åUY eqcœm\`clypsdc[+ƒ sd pcœmabclsayph3eâz3y+\`\`ajcl\`szclm[p cib[_å cl\l ãv ;absaijcœype;s ^d[jh;clåä\dc m[ Z;abh3Y+^dab[Ph#Zc^>å~cclhÙabh3eqabÎateq 3YPibs~Y+hpe ƒ½yøˆp[ \`sah;cåêsd clmabcls ƒ [P\` Y_^`aj[ h èn~^^` ;cwchpel[+ƒqym\`absdats ^d ;cwzpy+\`\dabc\]s9y+\`c \dcœs>^`[p\`cle Y+hpeY ;abkp QhI 3 Zc\[+ƒ~sR clmajcœslc c\`kpc ãv ;c Zc 3Y؈ ab[p\[+ƒ ^d 3cQsdáqs>^`c abs^` I ps#^`[)ƒ½yøˆ [P\Ùcl c\`kpchpmc{[pƒ h;cå sd clmabcls abhê\dcœsr [PhpsRc^`[Î^d ;c p[ ; ;ity_^`aj[ hêiby m]ì)[pƒy e;y+ ;^`Y_^`aj[ h Tn s [Pabh ^`cle[p q^vz áùz{y+^datmñ ï Ÿl P u ñ ^` ;atsvâabkp I^vZpcYâ [ sr sdajz;ibc c q ;ibyph3y_^`aj[ h{ï½y+^ [Pibclm ;ibyp\ s`mypijc ñ ƒ [P\A^d ;clsd pcœmabclsae;á h3ypâatms [PZpsRcl\dˆ cleâajhùƒ [ s`srabi3\`clm[p\]e9 ãv ;clsdc 3Y+^R^`c\`h3s Ih3YPâcŒe ír 3 ;h3m ^` 3Y_^`cle cl I ;abijabz;\`aby î; _\`cˆpcœy+ii [ sr^sd pcœmabcls abhâsr^`y sratsƒ [ i ib[_å cœevz ály+z;\` ; q^ Y+ ; clyp\`yph3mc [Pƒ h3cåoibáeqcl\dabˆpcœesr clmajcœswï½æai eq\`cleqk cjöè [P ;ite Ÿl žpñ à ƒ m[ ;\`sdcp ;^d ;ats á [+^d 3clsdabsO 3sR^ ZcVm[ hqo3\` cle Z á⃠;\d^d ;cl\ sr^d 3eqabclsvsd ;[_åoabh;kl^d 3Y+^ ^` ;atsa [qeqci m[ ;ite)zc{y+itsr[îyp ; ;ibajcœe)^`[q^d ;c$clˆp[pib q^`aj[ h&[pƒv 3i ^`abmcibij ;ity+\ [P\`k YPh;atsR sl Results showed that in "normal" situations the population, the number and the mean stress tend to stabilize over the time. The evolution leads to a population composed of individuals well adapted to their environment spread over a few number of. When environmental difficulties appear, results show a decrease of and barriers become lower. This leads to new recombination between individuals and favors new formation. At the end of a crisis, the barriers are restored and a high number of emerge. The behavior of the system is thus to favor emergence of new in response to the population lack of adaptation. As pointed by (Matic, Rayssiguer, Radman 1995), this might be a possible explanation (at molecular scale) for the dynamics observed in fossil record. These patterns, named "punctuated equilibria", reveal most in stasis followed by abrupt appearance of newly derived g=h#[p ;\~c q c\`aj clh ^]s ^d 3c o3hpy+iósr clmajcœsah ; (Eldredge, Gould 1972). Of Zpcl\ 3Y sazcclh course, this hypothesis must be confirmed by further studies showing that this model could be also applied to the evolution of multicellular organisms. In our experiments, the final number has been always greater than one (with exception of some complete population extinctions). This property appears to be significant in comparison to previous artificial ecosystem studies. In Gaïa (Gracias, Pereira, Lima, Rosa 1996), GraciasåO ;cl\dc observed ajhpeqajˆ ateq 3YPibs 3Y؈ c^d[o3h3ey# Y_^`ajh;kç 3YP\R^d that cohabitation between two never occurs, even when beginning with two highly adapted. The explanation of this phenomenon is that, in a system where individuals have to find a mating partner, the probability of achieving reproduction is Y+ibåvYØá sjkp\`cly_^`c\ ^d 3YPhÈ[Ph;cQï åoaj^d &c ;mcl q^dab[phè[pƒ sr[ cm[ â ;ibc^`cj p[ ; ;ity_^`aj[ hçc ^dabh3m ^`aj[ h3s ñ ~ãv 3absO 3\d[ pcl\r^>áçy+ ; clyp\`s~^`[ Zc srabkph3a opmly+hi^ ajh#m[p 3YP\datsR[ hj^`[ ;\dclˆ aj[ 3s Y+\d^dajopmatY+i3clm[IsRáqsR ^dcl sr^d 3eqabclsl ýg=hé LŸ ty; \`Y matypsqï \]YPmabY s ŸŒ P ñ [PZpsRcl\dˆ cleô^d py_^çm[p 3YPZ;aj^`Y_^`aj[ hêzc^>å~cchê^>å [ôsr clmajcœsùh;clˆpcl\ [qmm ;\`sl AclˆPclh&åO ;clh&zck ajh3h;ajh3kîåoa ^` &^>å~[q ;ajk ;ibá)ype;yp q^dcœe sd pcœmabclsl Wãv ;cc q ;ity+h3y+^dab[ph[+ƒ ^d ;atso ; ;clh;[p clh;[phçabso^d 3Y+^l ;abh YÙsdáqs>^`c h;cl\l 9^` ;c ;\`[PZ3YPZ;abijaj^>á$[+ƒvYPm] ;abcˆ abh;k\`c 3\d[qeq 3m^dab[PhabsL ;abkp 3ijá eqcl pclh3e;y+hi^{[ hu^` ;cèh ; Zpcl\$[+ƒ ajh3e;ajˆ ateq 3Y+its$[Pƒ ^` ;c)s`y+ c behavio As poi might b the spe pattern derived hypoth that thi multice In our always populat signific studies Gracias never adapted that, in partner highly same s compet In con differen of spec to each crisis p a value The str individ an envi the stre as a ki

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