I have read  and I don't buy it     Because genetics influence susceptibility to migraine, it can be   shaped by evolution. Fitness-impairing disorders, including severe   headache, tend to disappear as a result of natural selection, and   their frequency decreases to near the rate of spontaneous   mutation. However, migraine has not   diminished over millions of years of evolution. Its prevalence has at   least been maintained at a high level, and has even been shown to be   increasing.   This phenomenon suggests that a central nervous system (CNS)   susceptible to severe, intermittent headache has been linked to an   important survival or reproductive advantage.   the argument in wiki is equivalent to since we know that evolution is correct - it means that headaches must benefit us somehow otherwise we wouldn't have it so let's think of some reasons - which is in my opinion is a fallacy.  I could believe that this is a bad side effect of some more efficient to survival trait like being smart, ()     Finally, migraine may be a component of imperfect central nervous   system design. Evidence has suggested a dysfunction of pain-inhibitory   pathways in migraine and discordant interaction between the ancient   brain stem design and the more evolved neocortex.   EDIT:  I have read the  and , and I agree that they do partially answer my question in regard that a mild 'badness' can get past. I would argue that my question is different in a way that I am referring to specific point The trait might have a tradeoff which essentially makes no change to the overall fitness  The way I understand it is that one gets some 'perk' that is beneficial in some situations and disadvantageous in others and they cancel each-other out. (I just don't see how without some huge benefit migraines would get past). What I am asking is what so advantageous we must have gotten - that such horrible thing like migraines got through.  Are there any studies done - that incapacitating migraines are coupled with an evolutionary trait?
If a trait would be advantageous to an organism then why hasn't it evolved yet?  Conversely, if a trait is not advantageous or mildly disadvantageous, why does it exist?  In other words why does evolution not make the organism more "perfect"?    This is a general question that would be applicable for any kind of trait. Please keep the answers precise and scientific.   Read this meta post for more information:
Why are memory statistics in top and htop different? Whenever I use top and htop commands to see memory stats, they are always different as shown in figures. Which should I trust? I am trying to understand how to see the total size of my hard drive &amp; how much is left. It was recommended on various searches to use the command below   df -h Filesystem      Size  Used Avail Use% Mounted on udev            7.8G     0  7.8G   0% /dev tmpfs           1.6G  9.6M  1.6G   1% /run /dev/sda1       219G   29G  180G  14% / tmpfs           7.8G   18M  7.8G   1% /dev/shm tmpfs           5.0M  4.0K  5.0M   1% /run/lock tmpfs           7.8G     0  7.8G   0% /sys/fs/cgroup cgmfs           100K     0  100K   0% /run/cgmanager/fs tmpfs           1.6G   64K  1.6G   1% /run/user/1000   However I don't understand any of these directories. I mean what are they, are these all directories or partitions or what? And why do they appear under "mounted on"? How does that bit work. I assume the /dev/sda1 is my solid state drive? So now if I install applications, which one of these directories does my software get installed  into? I assume it just gets installs in the / directory (I haven't even got a clue what the / directory is). Can someone explain what the other directories are and what they are used for? I'm trying to change the cpu frequency on my laptop (running Linux), and not having any success. Here are some details:    # uname -a Linux yoga 3.12.21-gentoo-r1 #4 SMP Thu Jul 10 17:32:31 HKT 2014 x86_64 Intel(R) Core(TM) i5-3317U CPU @ 1.70GHz GenuineIntel GNU/Linux  # cpufreq-info cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009 Report errors and bugs to cpufreq@vger.kernel.org, please. analyzing CPU 0:   driver: intel_pstate   CPUs which run at the same hardware frequency: 0   CPUs which need to have their frequency coordinated by software: 0   maximum transition latency: 0.97 ms.   hardware limits: 800 MHz - 2.60 GHz   available cpufreq governors: performance, powersave   current policy: frequency should be within 800 MHz and 2.60 GHz.                   The governor "powersave" may decide which speed to use                   within this range.   current CPU frequency is 2.42 GHz (asserted by call to hardware). (similar information for cpus 1, 2 and 3)  # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors performance powersave   I initially had the userspace governor built into the kernel, but then I also tried building it as a module (with the same results); it was loaded while running the above commands (and I couldn't find any system messages when loading it):  # lsmod Module                  Size  Used by cpufreq_userspace       1525  0 (some other modules)   And here are the commands I tried for changing the frequency:  # cpufreq-set -f 800MHz Error setting new values. Common errors: - Do you have proper administration rights? (super-user?) - Is the governor you requested available and modprobed? - Trying to set an invalid policy? - Trying to set a specific frequency, but userspace governor is not available,    for example because of hardware which cannot be set to a specific frequency    or because the userspace governor isn't loaded?  # cpufreq-set -g userspace   Error setting new values. Common errors: - Do you have proper administration rights? (super-user?) - Is the governor you requested available and modprobed? - Trying to set an invalid policy? - Trying to set a specific frequency, but userspace governor is not available,    for example because of hardware which cannot be set to a specific frequency    or because the userspace governor isn't loaded?   Any ideas? Does "minor revision" mean "accepted with minor revision"? I just received a decision letter from a journal editor (after three rounds of major revision). The letter shows that the reviewers "have asked for some other minor revisions". After getting the minor revision letter, I immediately completed the revision in accordance with the feedback from the reviewers (the suggested changes just involve adding a few sentences) and immediately resubmitted the revision to ScholarOne. A week has passed since I submitted the revision, but the status in ScholarOne remains unchanged. Is this normal? Can I assume that this basically means "acceptance with minor revision"? Thanks for your insight and sharing. Is there an easy way of getting the charset and collation of the DB tables in WordPress without resorting to SQL queries? $A$ is normal and nilpotent, show $A=0$ Given a matrix $A \in R^{n \times n}$ which is normal ($AA^H=A^HA$ where $A^H$ is hermitian of $A$) and nilpotent ($A^k=0$ for some $k$). Now we need to show that $A=0$. (This is essentially exercise 5(b) in sec. 80 on p.162 of Paul R. Halmos' Finite-Dimensional Vector Spaces.) I tried to show in the following way, we know that, $AA^H=A^HA$ pre-multiply by $A^{k-1}\implies A^kA^H=A^{k-1}A^HA$ Now, we have $0 = A^{k-1}A^HA$, since $A$ nilpotent. I am not sure how to proceed from here to show $A=0$. Can someone help me in this problem? Enumerate after \label I have the following code:  \usepackage{hyperref} \newtheorem{thm}{Theorem}  \begin{thm} \label{mythm}    \begin{enumerate}       \item     \end{enumerate} \end{thm}  \ref{mythm}   The ref prints the right number. However, when I click on it, it will lead me to a wrong page (basically, to the beginning of the document).  pdflatex also has some warning.  If I add $ $ between \begin{thm} and \begin{enumerate}, the problem disappears, but now, the enumeration starts a new line.  Is there any way to fix this? Duplicate user in reputation league So I understand that this has happened in the past: , but all of the &quot;duplicate&quot; posts are marked as  so here is a new bug report: On the , I am listed twice:  While that's fun and all, it isn't exactly right. Isn't the uncertainty principle just non-fundamental limitations in our current technology that could be removed in a more advanced civilization? From what I understand, the  states that there is a fundamental natural limit to how accurately we can measure velocity and momentum at the same time. It's not a limit on equipment but just a natural phenomenon.  However, isn't this just an observational limit? There is a definite velocity and momentum, we just don't know it. As in, we can only know so much about the universe, but the universe still has definite characteristics.  Considering this, how do a wide range of quantum mechanical phenomena work? For example, quantum tunneling - its based on the fact that the position of the object is indefinite. But the position is definite, we just don't know it definitely. Or the famous light slot experiment? The creation of more light slots due to uncertainty of the photon's positions?  What I am basically asking is why is a limit on the observer, affecting the phenomenon he is observing? Isn't that equivalent to saying  because we haven't seen Star X, it doesn't exist? It's limiting the definition of the universe to the limits of our observation! What are drawbacks or disadvantages of singleton pattern? The  is a fully paid up member of the 's , but it lately seems rather orphaned by the developer world. I still use quite a lot of singletons, especially for , and while you have to be a bit careful about multithreading issues (like any class actually), I fail to see why they are so awful.  Stack Overflow especially seems to assume that everyone agrees that Singletons are evil. Why?  Please support your answers with "facts, references, or specific expertise" How should ambiguous tags be dealt with? If tag "foo" refers to two or more different technologies or concepts is it better to retag the less common usages or is it better to add additional tags to disambiguate?  My particular issue is with the  tag which mostly refers to the  but could also refer to the  programming language &amp; software platform. Is it better to retag the Curl language questions as  (any other suggestions?) or add some other tag such as "language"? Gparted: move extended partition on the left I have some free disk space on the left of my ubuntu (sda5)  What is best solution to extend sda5 ?  I can    copy sda3 or sda5 with dd to bigger disk. delete sda3,5,swap create sda3,5,swap dd original partition.   Not sure how to do it properly.  May be there is a simpler solution. I just enabled the Blenderkit addon but cannot seem to figure out how to edit the objects. I looked in this reddit thread and amazingly none of the solutions worked for me.  Making it a single user object, data, and materials did not work. I do not see any option to append when adding a model form the Blenderkit asset bar (I even tried saving it and appending the object in another instance of Blender and it still would not let me edit it). And when I right click I do not see an option to make local on outliner collection. I am using Blender 2.83 if that makes a difference but can use 2.9 if need be. Any other solutions? paragraph numbering I am using the paragraph section head, i.e.,   \paragraph{This is a cool paragraph}    I would like it to compile with numbering. If I change the secnumdepth (i.e., \setcounter{secnumdepth}{4}) this will work, but produce the "wrong" type of numbering, i.e.,      1.1.1.1 This is a cool paragraph      1.1.1.2 This is another cool paragraph etc.   What I would like is      1 This is a cool paragraph      2 This is another cool paragraph   or, if not,      1.1 This is a cool paragraph      1.2 This is another cool paragraph   where the first 1 indicates the section number and suppresses the subsection and subsubsection numbers. Can this be done? Other ways to say "I have a bad hunch" I'm looking for ways to say "I'm having a bad hunch", or more like a bad feeling about something upcoming. The gut-wrenching feeling that something bad will happen. For each positive integer $n$, let $x_n=1/(n+1)+1/(n+2)+\cdots+1/(2n)$. Prove that the sequence $(x_n)$ converges.   This is what I have so far..  Let $\epsilon &gt; 0$ be given to us. We must show that there exists an $N \in \mathbb{N}$  such that $n\ge N \implies \left|\frac{1}{2n} - 1\right| &lt; \epsilon$. Choose $N$ to be any positive integer which is larger than $\frac{1}{\epsilon}$. (So $N&gt;\frac{1}{\epsilon}$.) Then $n\ge N \implies \left|\frac{1}{2n} - 1\right| = |\frac{1-2n}{2n}|$ Custom setting Setting type not visible I need to show that for prime numbers of the form $p=4n+1$, $x=(2n)!$ solves the congruence $x^2 \equiv-1\pmod p$. I then need to show this implies p isn't a gaussian prime.   I have started to solve this using Wilson's theorem that a number $z$ is prime iff $(z-1)!\equiv-1\pmod z$. Therefore the endpoint of my proof should be that $(p-1)!\equiv-1\pmod p$.  As $p$ is of the form $p=4n+1$, I only need to prove that $4n!$ is congruent to $-1$ modulo $p$.   Here is my working so far: Starting with the congruence $x^2 \equiv -1\pmod p$:    $$\eqalign{x^2 = -1\pmod p&amp;\implies   x^2 + 1 = kp \implies (x-i)(x+i) = kp\cr &amp;\implies ((2n)!-i)((2n!)+i))=kp \implies 4n!- 1 =kp\cr}$$   This is where I start to run out of any ideas that seem to get me anywhere. Any tips would be greatly appreciated! Share a Folder between two Local Users I and my brother have User Accounts on this machine. I want to share the Documents directory with him.  Is there a STRAIGHTFORWARD way to do it?  I am not a power user so I am looking for a way to do this using nautilus, rather than a script or a way that requires creating symlinks.  I can download an application if i have to.  Last time I wanted to do this I just copied the contents to /home for both of us to use.  Something I can do in System Settings would be appreciated What is the syntax for IF/ELSE in bash? I am trying to pull logs and doing few others things directly. written a small line BASH but not working. I am sure thats with IF Condition.    sed -rne '/21:25:07/,/21:50:07/ p'  server.log.2015-04-21 &gt; /tmp/filename.log ; du -sh  /tmp/filename.log ;  if [`du -sh  /tmp/filename.log` -gt 0] then gzip /tmp/filename.log ;