
Lenia – Biology of Artificial Life - p1esk
https://arxiv.org/abs/1812.05433
======
veddox
Hm, sounds like mathematician giving fancy biological-sounding names to some
procedurally generated abstract art forms.

Frankly, I had hoped for more, given the title. There's some really cool work
that has been done with digital artificial life that has real biological
significance. For example, Richard Lenski's group at Michigan State University
developed a platform called AVIDA
([https://en.wikipedia.org/wiki/Avida](https://en.wikipedia.org/wiki/Avida))
that has been used for evolutionary biology research. Slightly different, 2012
saw the publication of the first whole-cell computational model
([https://www.sciencedirect.com/science/article/pii/S009286741...](https://www.sciencedirect.com/science/article/pii/S0092867412007763)).
And in the past 30 years, computer simulations of ecosystems have slowly been
gaining momentum and acceptance as a tool for addressing ecological questions
that are very hard to study in real life (this happens to be the field I work
in).

Lenia, on the other hand, is nothing more than an abstraction of Conway's Game
of Life. A pretty mathematical pastime that is fun to play around with and
gives you some interesting patterns - but nothing that merits the description
"biology". The whole paper just reeks with misapplied terms: from "taxonomy"
to "ecology" and even "physiology". (They don't have anything to do with their
real counterparts.) In short, I fail to find any significance for our
knowledge of life on earth, or any other life, for that matter.

Pretty graphs, though.

~~~
trevyn
Molecular biology:
[https://youtu.be/_SGoDIkscXg?t=39](https://youtu.be/_SGoDIkscXg?t=39)

Game of Life: [https://youtu.be/xP5-iIeKXE8](https://youtu.be/xP5-iIeKXE8)

Sure, one is 2D and discrete, the other is 3D and continuous... oh wait, Lenia
is 2D and continuous. That’s interesting.

~~~
veddox
My comment had nothing to do with the number of dimensions or whether the
world is continuous or discrete. (AVIDA and many other biological models are
both 2D and discrete.)

The two core characteristics of life are metabolism and reproduction.
Metabolism requires some kind of input, a resource, that is somehow consumed
or transformed as the organism grows or is active. Reproduction places an
organism in a long line of descent, possibly with mutation and evolution, akin
to what we like to call Life.

Sure, living organisms show (symmetrical) organisation - but that is because
this morphological organisation enables metabolic functions and reproductions.
The morphology does not arise because of some random mathematical rules, but
because it fulfills a specific need. It is not an end in itself. This
teleological perspective is completely lacking in cellular automata such as
Lenia.

 _(edited for clarity)_

------
oblosys
Youtube video showing some of the persistent life forms:
[https://www.youtube.com/watch?v=iE46jKYcI4Y](https://www.youtube.com/watch?v=iE46jKYcI4Y)

------
whatshisface
Here is an implementation:
[https://chakazul.github.io/Lenia/JavaScript/Lenia.html](https://chakazul.github.io/Lenia/JavaScript/Lenia.html)

Here is the github:
[https://github.com/Chakazul/Lenia](https://github.com/Chakazul/Lenia)

------
lioeters
Strange and fascinating. It raises interesting questions about we consider
"life". The implementation [0] contains a whole taxonomy tree of variations,
of which Conway's Game of Life is but a branch. It's certainly an ecosystem of
mathematical "life" forms.

Reminds me of one of my favorite books, Vehicles: Experiments in Synthetic
Psychology [0].

[0]
[https://chakazul.github.io/Lenia/JavaScript/Lenia.html](https://chakazul.github.io/Lenia/JavaScript/Lenia.html)

[1]
[https://mitpress.mit.edu/books/vehicles](https://mitpress.mit.edu/books/vehicles)

------
fao_
The title reminds me of the work done by Karl Simms and published in
SIGGRAPH94

[http://www.karlsims.com/papers/alife94.pdf](http://www.karlsims.com/papers/alife94.pdf)

[http://www.karlsims.com/papers/siggraph94.pdf](http://www.karlsims.com/papers/siggraph94.pdf)

(video here:
[https://archive.org/details/sims_evolved_virtual_creatures_1...](https://archive.org/details/sims_evolved_virtual_creatures_1994))

------
ambrop7
I wonder if cellullar automata could exhibit at least some approximation of
classical mechanics, i.e. mass, inertia, forces etc.? From my understanding,
motion as seen here is purely due to the structure of the objects.

~~~
no_identd
Yes. See here:

[https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.56.1505](https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.56.1505)
Frisch, Hasslacher, Pomeau - Lattice Gas Automata for the Navier-Stokes
Equation (1986)

Citations (5k+) here:

[https://scholar.google.com/scholar?cites=5993777633272177716](https://scholar.google.com/scholar?cites=5993777633272177716)

See also my other comment here:

[https://news.ycombinator.com/item?id=18757946](https://news.ycombinator.com/item?id=18757946)

------
kvark
Huh, they extend the Game of Life with a complex neighbor kernel, and get more
complex patterns emerging. This is a cool experiment, but hardly "biology of
artificial life".

~~~
veddox
A short, sweet summary of my opinion :D

------
whatshisface
> _We describe the methods of constructing and studying Lenia, including its
> mathematical definition, in silico simulation [...]_

It's funny how different fields of science have all invented their own names
for "computer program." Physicists and many engineers call them "codes," and
biologists love fitting in the buzzword "in silico."

~~~
tokai
I would guess it's a play on in situ.

~~~
taneq
Or 'in vitro' ('in glass' ie. 'in a test tube'), as opposed to 'in vivo' ('in
life').

~~~
veddox
Yes, in biology we use _in silico_ to extend this previous distinction between
_in vivo_ and _in vitro_.

------
hirundo
I honestly don't know if this a simulation of life or an example of it. Or if
those are mutually exclusive.

~~~
taneq
From the video, they seem to be more like stable moving patterns than life.
They don't appear to self-reproduce or have behaviours.

~~~
AareyBaba
That is in the future works section in the pdf.

 _8\. Do self-replicating or pattern-emitting lifeforms exist in Lenia?_

~~~
taneq
It seems kind of a stretch to call it "biology" then.

"I designed a new life form! _points to lego brick_ It exists and you can move
it! Future work will involve making it self-replicate and have artificial
intelligence."

------
dkural
Figure 20 from the paper is particularly interesting. Life solves multiple
problems, and for unicellular life, one of them is the problem of locomotion.
At least here Lenia and real world biology seems to have some amount of
overlap.

~~~
ianai
If there’s any overlap at such a simplified model then the simplified model
just might be a good place to start figuring out the actual system.

~~~
veddox
All due respect - I think that for pretty much any simple shape you'll find an
actual organism that "looks just like it".

~~~
dkural
I do tend to agree that unicellular life has a mind boggling diversity of
forms and you can find similarities to most things, simple or not-simple :)

That said, humans have a very specific notion of "simple shape", intuitively
incorporating symmetry into it. Symmetry is far from guaranteed in mathematics
(although mathematicians, being human, also tend to search and study symmetric
things). Even in the most symmetric objets - let's say groups, there are many
more non-abelian (i.e. not commutative a _b != b_ a) groups than there are
commutative groups.

------
no_identd
Pet Peeve Rant:

Just like in the case of SmoothLife (which Lenia generalizes), the square grid
used for this implies a lack of isotropy(we could also say that it "introduces
anisotropy"; but that makes it sounds like a good thing), EVEN IF you turn the
entire thing continuous like done here and use . This last fact becomes
relatively obvious if you mash the "random" button in the demo, you'll see
'square' noise.

This really ought to use a triangular grid (or the dual of it, a hexagonal
one) to ensure isotropy; Frisch, Hasslacher & Pomeau showed this in 1986 while
working on two dimensional Navier-Stokes equations:

[https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.56.1505](https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.56.1505)
(Ctrl+F isotropy)

Section 4.4.4 of the OP paper DOES acknowledges that one could generalize this
further (which includes generalizing to a hexagonal grid, doesn't mention a
triangular grid however), but unfortunately it doesn't mention isotropy even
once, anywhere, not even in section 3.1.1 on Spatial invariance (albeit, I
suppose, the section does semi-address it indirectly, but what's described
there to address it seems like a hack, and the 'empirical' evidence from the
random button would seem to agree with it.).

Having said all that:

I still consider Lenia DAMN impressive, and I think other people have pointed
out this lack of isotropy to the author before. I suspect he'll follow up with
more generalizations, but, based on the Github activity (See here:
[https://github.com/Chakazul/Lenia](https://github.com/Chakazul/Lenia) \- last
commit in July, long open & relatively trivial pull requests, etc.) and when
the OP paper got published to arXiv, I suspect he's been busy writing the
paper & with other academic duties and that he could almost certainly use a
lot of help with this project. I lack the time (and admittedly, skills) to do
so, but I figure if I point this out here, maybe some people might want to
pick up on it, especially since, as the author points out, Lenia & further
generalizations of it could serve as a great benchmark for various machine
learning related matters, which Hacker News users seem to have a great
interest in.

Edit: I've decided to us this opportunity to do some renewed literature
research:

1.

A:

If you want to read more about Euclidean automatONS beyond the citation #27
from the OP paper, you might want to check here (I suspect the author of the
OP paper either overlooked the existence of this book chapter, or hasn't had
time to study it yet):

[https://link.springer.com/chapter/10.1007/978-1-84996-217-9_...](https://link.springer.com/chapter/10.1007/978-1-84996-217-9_12)
Pivato, Marcus - RealLife (Chapter from "Game of Life Cellular Automata"
edited by Andrew Adamatzky)

Which seems like a follow up work to:
[https://arxiv.org/abs/math/0503504](https://arxiv.org/abs/math/0503504)
Pivato, Marcus - RealLife: the continuum limit of Larger Than Life cellular
automata

B: There also seems to exist a separate idea ALSO called Euclidean AutomatA,
first described here:

[https://www.aaai.org/ocs/index.php/SSS/SSS14/paper/viewFile/...](https://www.aaai.org/ocs/index.php/SSS/SSS14/paper/viewFile/7696/7742)
Kornai, András - Euclidean Automata

Citations here:
[https://scholar.google.com/scholar?cites=2906127536931309801](https://scholar.google.com/scholar?cites=2906127536931309801)

The author of this seems unaware of the works by Pivato, the same applies to
this follow up work:

[https://ruj.uj.edu.pl/xmlui/bitstream/handle/item/51661/EA01...](https://ruj.uj.edu.pl/xmlui/bitstream/handle/item/51661/EA01.pdf?sequence=1&isAllowed=y)
Gyenis, Zálan - Skeleton in the Euclidean closet

2\. More on Triangular & Hexagonal automata:

A:

Research by Carter Bays:

[https://link.springer.com/referenceworkentry/10.1007%2F978-1...](https://link.springer.com/referenceworkentry/10.1007%2F978-1-4939-8700-9_58)
Cellular Automata in Triangular, Pentagonal, and Hexagonal Tessellations

"First Online: 28 November 2018" \- but this is basically a republication of a
2009 version of an expanded & updated version of
[http://wpmedia.wolfram.com/uploads/sites/13/2018/02/15-3-4.p...](http://wpmedia.wolfram.com/uploads/sites/13/2018/02/15-3-4.pdf),
which stems from 2005!

Citations of the 2005 version (doesn't seem directly listed in Google
Scholar):

[https://scholar.google.com/scholar?q=%22A+Note+on+the+Game+o...](https://scholar.google.com/scholar?q=%22A+Note+on+the+Game+of+Life+in+Hexagonal+and+Pentagonal+Tessellations%22)

Citations of the 2009 version:

[https://scholar.google.com/scholar?cites=1062581570709413178...](https://scholar.google.com/scholar?cites=1062581570709413178&as_sdt=2005&sciodt=0,5&hl=en)

And there's also an even older version from 1994, only addressing triangular
tesselations:

[http://wpmedia.wolfram.com/uploads/sites/13/2018/02/08-2-4.p...](http://wpmedia.wolfram.com/uploads/sites/13/2018/02/08-2-4.pdf)

Citations here:
[https://scholar.google.com/scholar?cites=9274761406110052964](https://scholar.google.com/scholar?cites=9274761406110052964)

B:

Research by Andrew Wuensche:

[http://users.sussex.ac.uk/~andywu/downloads/papers/self_rep....](http://users.sussex.ac.uk/~andywu/downloads/papers/self_rep.pdf)
Self-reproduction by glider collisions: the beehive rule

Citations here:

[https://scholar.google.com/scholar?cites=1226081815033511695...](https://scholar.google.com/scholar?cites=12260818150335116959)

On an off-topic side note: Navigating citation space is an absolute mess, as
the above shows. Researchers constantly have to cut corners when it comes to
studying the literature because it's too damn hard to navigate, which leads to
constant overlooking of convergently evolved research. A Peter Landin quote
comes to mind:

"Most papers in computer science describe how their author learned what
someone else already knew."

If this bothers you even nearly as much as it bothers me, I suggest you see
how you can help the Initiative for Open Citations:

[https://i4oc.org/](https://i4oc.org/)

So tools like [http://citationgecko.com/](http://citationgecko.com/) &
[http://cluster.cis.drexel.edu/~cchen/citespace/](http://cluster.cis.drexel.edu/~cchen/citespace/)
can actually help put an end to this mess.

~~~
pmayrgundter
Great comments! Thanks for posting. I've written a hex grid automata for
wolfram simulations in java, js & dart before.. maybe I can get it contributed
to the Lenia guys.

[https://github.com/pablo-
mayrgundter/freality/tree/master/ph...](https://github.com/pablo-
mayrgundter/freality/tree/master/phys/fluid)

------
sytelus
TLDR; "Artificial life" is a misnomer for efforts like this which are simply
play on cellular autometa type variations. This phrase is extensively used by
biologist to constructing actual living physical cells using non-living
material. This paper is not about that and I hope folks stop calling this
"artificial life".

Important bit:

 _Life can be defined as the capabilities of self-organizing (morphogenesis),
selfregulating (homeostasis), self-directing (motility), self-replicating
(reproduction), entropy reduction (metabolism), growth (development), response
to stimuli (sensitivity), response to environment (adaptability), and evolving
through mutation and selection (evolvability). Lenia, the subject of this
paper, is able to achieve many of them, except self-replication that is yet to
be discovered._

Above definition wouldn't be agreed upon by many biologist because the entire
concept of _environment_ that is as complex as universe is missing. It's easy
to create something that can "thrive" in 2D grids with bunch of simple rules
but quite another thing that can thrive in a computer called _universe_ which
is simulating 10^80 atoms at once where all quantum and space-time rules
aren't even known to us.

~~~
dj-wonk
However you would prefer the term be defined and used, for decades, people
have used the term "artificial life" to include cellular automata.

Sources:

[https://en.wikipedia.org/wiki/Artificial_life](https://en.wikipedia.org/wiki/Artificial_life)

[https://en.wikipedia.org/wiki/History_of_artificial_life](https://en.wikipedia.org/wiki/History_of_artificial_life)

~~~
ianai
Further, the study of how life arises has to start somewhere very simple, like
drastically simple/simplified 2D rule systems.

